Exactly or precisely?
I’d say he’s being accurate about his peeve. 
This is one of mine too.
Although I recall a fun thread we had some years ago with a confused person who wanted to do conversions with infinite precision for … reasons, and could not comprehend, at all, the notion of significant figures or error bars on measurements.
Shortly after we moved and all our shit was still in boxes, my wife and I would say that we could locate an item with 100% accuracy, but with a precision of forty feet.
Yeah, but how fast was it going?
Or for that matter the ancient proof that some proportions are irrational.
This is what the Heisenberg Compensators are for, duhh.
No toilets in your new place? Huh.
I love this and I am going to use it if I am ever in a situation where I need to describe a boulder.
Boulder-sized boulders are the reechest kind!
I’m aware of the concept of significant figures. But is there a term for an error caused by ignoring significant figures when converting units of measurement?
“We definitely put the pool in a mine for shielding. It was absolutely not to hide it from the funding people.”
“Don’t ask about the yellow neutrinos.”
Mars Climate Orbiter?
MCO for short.
No, that was a different error; one caused by not being aware of what units were being used.
To give an example of what I’m asking.
John is at Bob’s house. He asks Bob how far away Bill lives. Bob says Bill lives thirty-two thousand, one hundred and eighty-seven meters away.
John remarks that it’s extremely unusual that Bob knows how far away Bill lives, down to the meter.
Bob says he just did the math. Bill once told him that his house was twenty miles away from Bob’s. Bob knows that there are 1609.34 meters in a mile, so he multiplied that figure by 20 and the result is their houses are 32,187 meters apart.
John could say “Bob, you made an error caused by the misuse of significant figures.” But it’s quicker if John says “Bob, that’s a **** error.”
Is there a term that replaces ****?
Unit conversions are simply multiplication, and the significant figure rules cover multiplication just fine.
Note that when you convert units, you are multiplying by conversion factors that all equate to one. Such as:
1 inch = 2.54 centimeters
Divide both sides by 2.54 cm, and you get:
\frac{1 inch}{2.54 cm}=1
You can then multiply any measurement in cm by this conversion factor, and it’s the same thing as multiplying by one.
15 cm \left( \frac{1 inch}{2.54 cm} \right )= 5.9 inch
Some conversion factors have significant figures as well, and some are infinitely precise, like exact equivalencies. An example of the latter is 1 foot = 12 inches. Another one is 1 inch = 2.54 cm (i.e. 1 inch is defined to be exactly 2.54 cm.)
So here we are limited by the number of significant figures in the original measurement, not the conversion factor. The original measurement of 15 cm has two significant figures, so the final result should also have two significant figures (5.9 inches).
Dumbass.
**** = imaginary precision fallacy.
ETA: I made the term up, but it is what it is.
ETA 2: dumbass precision fallacy sounds fitting too.
Ironically, given the circumstances, I was looking for a term that was more precise.
Either “significant figure error” or “error in precision,” I would say.