I grew up in Wayne and Oakland Counties. Put me down as never having heard the term either.
Never heard the term, nor any other term to describe how I always park.
Skipping over all the responses to post:
Never heard of “granny parking” before. Context would probably help a lot if I just happened on the term in an actual conversation, but absent that … sounds like it means “general bad parking job, car cockeyed in the parking space, etc.” Will check my first impression above.
Oh no … the term “granny parking” is unknown local to the SE Louisiana area, except perhaps to those who have lived in other areas.
Pulling through an open spot to face outward is simple enough … but backing in to a parking spot is challenging enough that wouldn’t expect “grannies” to attempt it all that much.
Never heard the term before, not in the Midwest or the Pacific NW.
I would think that “grannies” would be the least likely to attempt that maneuver, as so many people seem to have difficulty with it. However, I’m granny-aged myself, and park only that way, as it’s so much safer for everyone. Trying to back out of a space in a busy parking lot full of moving cars and rushing people is too dangerous.
That was my guess. I’ve always associated backing in with wanting a quick getaway (for Batman or anyone else, I guess).
I’d never heard the term before, and would have guessed it meant a very sloppy parking job, such as one that was so crooked that it took up two spaces. Except, of course, that nobody would ever recommend such a parking job.
Parking so you don’t have to back out is just good, sensible parking. Sure, it’s a little harder/less safe to back into a spot than to drive into it forwards… but it’s a lot harder/less safe to back out of a parking spot. Obviously everyone likes pull-through spots when they can get them, but when that’s not possible, it makes sense to back in.
I would also have assumed just a terrible job parking or driving in a parking lot. Rather like this old clip: Auntie Driver Parking Fail (subtitle) - YouTube
Parking those ways is so unremarkable that it’s odd there’s a term for it. Who even notices which way cars are facing?
I’ve heard that some people frown on backing into a parking space, on the basis that many people are not good at this and thus take a long time and/or end up with a sloppy result. I think it’s a useful skill you can acquire with only a bit of practice (for sure a camera helps).
But I’m surprised to hear that some people find “pull-through” parking objectionable, and am puzzled to think of any valid basis for this. Anyone know what this might be?
I do it whenever I can and the only problem is if someone tries to park in the spot in front as I’m pulling through. The few times that’s happened, I just stayed in the spot in back.
In my own apartment parking lot, many people park that way, this poster included.
A bit of context may help, in case anyone isn’t getting the mental picture. (It took me a while, and I never heard the phrase “granny parking”): We’re talking about pulling into a perpendicular parking space. Parking like this in a diagonal space is probably a bit more awkward, both getting in and out.
Pro-tip: Your side-view mirrors are your friends. Learn to use them for maneuvers like this.
Backing into parking spaces is discouraged or even forbidden in many places.
That’s not what I meant. I meant that it was in a parking lot. That was never mentioned in your OP. Being in a parking lot affects the range of choices from which one might have guessed. As it turns out, it doesn’t matter because apparently your wife is the only one who knows the term. I’ll bet it’s something she heard her father say a million times, so she assumed it was common usage.
That describes me perfectly. Never heard the term, but I would have assumed it meant something like just pulling in because there were two or three spaces in a row on a street.
I have an assigned space in my apartment garage. (Actually, I own it and get a separate tax bill for it, but never mind.) The guy in the next space always backs in. When he is gone I pull out through his space and if he is gone when I park I pull in through his space so I can front out. I guess I am technically trespassing since he owns his space too.
I, too, had never heard the term before, and I, too, would have assumed it meant “tentative, slow, and/or sloppy parking.”
I could believe this from the safety angle, and it seems like, in my area, backing into parking places has become more common lately.
That said, I think that backing out of a parking place is, for most drivers, probably easier than backing in, because you’re backing into an open space (the driving lane), rather than a space that likely has one or more solid obstacles (i.e., vehicles) defining it.
And, in my experience, many of the people who are now insisting on backing into parking places are really bad at it, having to take multiple tries to line things up (and often still doing it crooked or too far to one side). I have no doubt that some people can take to it quickly with a little practice, but I see many people who clearly need more than a little practice at it.
(Also, I sometimes see people insisting on backing into diagonal parking places, which is all kinds of dumb.)
And here there are many places which require it, such as the teacher parking by the elementary and middle schools. It’s probably safer for the children as the driver can see the children better.
This makes me happy to read. I wish that were a thing here. Every time I read of a person backing over a toddler in their own driveway, I want to scream “back-in parking”!
Aww…I’m sorry that you’re not tall enough to be a granny. 
Here’s what I found: When I back into my parking space, it makes a big difference if the adjacent spaces on the left and right have cars in them or are empty.
If either of the adjacent spaces are occupied, then it is very easy to back into my space and get it just right the first time, using the adjacent cars as reference points. (Hint: Keep you eye on your side-view mirrors.) But if both adjacent spaces are empty, then it’s much harder, because there is really no nearby object for reference. In that case, I have to open the door and look out at the pavement to see the line so I can use that as a guide.
(Side-topic: For parallel parking, whatever became of curbscrapers? Back in the before-times, cars all had curbscrapers.)
I keep my side-view mirrors tilted slightly lower than I ordinarily would, so that I can just barely see the pavement markings. It doesn’t mess with my normal use of the side mirrors in regular driving at all.