Do you work in a state government's IT department?
Why do you think this statement is true?
Neither of these statements can be true, as I've seen multiple examples of both. For what it's worth, one of the search terms you are looking for is "time theft" (as opposed to "wage theft"), the literature on this is also well developed as you might expect. And of course there are various types of related fraud (both in favor of employer and employee) which have been studied.
> I've never heard or read anyone make the point aside from myself.
This is plausible, but doesn't tell us much about anything but your own exposure.
Regardless , that wasn’t my point - far from being a novel idea there are lots of people looking at and arguing about it. Hell there is an industry around mitigations.
I'm not minimizing wage theft. It's a real issue. I'm just casting some doubt on the claim that it's the biggest form of theft by bringing light to a viewpoint most people haven't even ever considered.