I used something similar when I was a TA 20 years ago and while your assumption seems reasonable, there are actually a lot of different ways to solve even quite simple tasks and most cheating is very obvious on manual inspection.
I will also say that there’s problems where that is not the case. For example, we were told to write simulators for scheduling schemes (RR, MLFQ). Other than using different data structures (even that’s a bit of a stretch) not sure how much variance there will be.
Using the right tool for the right job is important.
Just above your post another author posted/cited results of a system that “never produced false positives”.
I think that cited number another author shared is probably correct but presumably, the tool is used in cases where problems are big enough to warrant it.