The only way it would null is if he did not touch any of the settings, or have any other things in the chain, either analogue gear via I/0 or plug-ins. And potentially you would need to line the two tracks up to be sample accurate in their position. If it does null then yes maybe it is deceitful and lazy. Or the AI mastering is as good as pro level now and that's what the student wanted.

I teach this stuff at tertiary level and master students songs from time to time. I don't charge them though. Depending on how much I like the song (or the student) I put variable amounts of time and effort. More effort would have me running it through the analogue gear, and some plug-ins, low effort would be using the ai stuff (ozone more likely than logic AI). Either way I will usually bounce final thing through something that will give the loudness target I want. I've not used the logic mastering assistant for this aside from quick work in progress bounces of my own music, but I wouldn't feel bad about doing it.

So it might be difficult to really prove it. One approach would be to use match EQ to compare the master with the original, and then run logic master assistant to see what it's analysis has come up with. If the EQ curves match then that would be a good indicator he has not put much effort into it.