We don’t have a dog but do frequently look after a neighbor’s beagle-Jack Russell terrier mix. She’s a sweet little dog, 13-1/2 years old. Her owner gives us the food to feed her, and the flavors vary. Chicken, bacon, beef, steak etc. But it sure does not smell like chicken, bacon, beef, steak etc. How do the makers of dog food know this is what the dog tastes? I can tell you that when given a choice between, say chicken-flavored dog food and real chicken, she will opt for the real stuff every time.
They don’t need to know. They could put chicken stock or chicken bits in it and then confidently say it was “chicken flavoured”, and maybe they do, but at the end day the dogs will eat pretty much anything and all the owners care about is that it says “chicken flavoured”. They’re not about to taste it to find out.
There are human tasters for pet food. Mary Roach discusses this in Gulp.
It needs to taste as advertised because some humans taste their pet’s food.
It is often flavored with chemicals the way much human food is. It’s flavor science!
One can only ask, “Why?!” 
My dog will eat the little tootsie rolls in the litter box if she gets to them - I’m pretty sure the taste of her food isn’t a consideration… But what do I know?
One of my dogs refused to eat peas. If anything he was given contained a single pea, that pea remained uneaten while the rest of the bowl was licked clean.
Same for pills. Capsules are easy but not so much tablet pills. I generally disguise by wrapping it in lunch meat. But if the meat is too loose or otherwise comes unwrapped to the point that exposes the pill to the taste sensors, the pill gets spit out to the floor.
The way most dogs inhale food you’d swear they taste nothing and care little about what they do taste. But they apparently do.
Guilty!
Hey, the way they snarf down those Milk Bones, I thought I might be missing a good thing.
I wasn’t. But they aren’t terrible either.
When I was a kid, I tried my Peke’s Gaines Burgers, because they looked really cool. Once was enough.
Our dogs will not touch a milk bone brand biscuit. They prefer the expensive ones. Makes it embarrassing at the bank drive through.
As for pet foods, read the label!
Maybe they pay little boys to dare each other. I know of one who tried cat food on a dare.
And to think I’m feeding my husband hot dogs. 
Our spaniel hesitates with new foods and treats and tentatively tastes before accepting them. This is contrary to the Labrador Creed - gulp now, ask questions later.
I was given a free sample 20 pound bag of sardine & herring dog food. Our dogs loved it, but the smell was off putting.
Once, I tried a kibble of dry cat food, just to see what it tasted like.
It was not good. At all.
The thing is, once I decided to try it, I was amazed how hard it was to actually bring the little bitty nugget up into my mouth. I had to force myself, and it took a few tries just for the one taste.
It’s amazing how strong food taboos are.
Kevin O’Leary, of Shark Tank game, says in his book his first post-MBA job was giving fanciful flavour names to cat food products all made from the same “putrid” meat and fish pastes. To get the job he had to eat the cat food in front of the executives while smiling and “licking his fingers for effect”.
Which is odd to me - it is a variety of food, after all. Just because it is created for dogs doesn’t automatically make it poison for humans.
For cats, actually, and that’s the thing I had to tell myself over and over to be able to do it.
I put the pill in my hand along with a half-dozen of those small training treats. My big goofy lab mix snarfs it all up.
IIRC from Roach, cats don’t care much about most flavors like turkey, but they go mad for taurine. Dog food doesn’t have enough taurine for cats’ health. If you’re wondering whether your cats will feast upon you when you are dead, taurine is found in large amounts in the brain, retina, heart, and blood.
My theory is that I would not feed anything to an animal that is plainly inedible (not talking about mere flavour profile preferences, or a hint of taurine or B vitamins). I tried a tiny morsel of the “good” cat food supposedly made from freeze-dried meat and it tasted like… a piece of chicken. Similar for the frozen dog food. Obviously there were no spices, salt, etc. On the other hand, a piece of cheap dry cat food indeed tasted like ass. And I saw someone feed a free sample of “beef”-flavoured “supplementary” food to a street cat and she was gobbling that stuff up, so there must have been salt or taurine or whatever in there because there was only 4% beef; same principle as human junk food.