> Cheaters, by definition, avoid real work, so they won't be using custom models unless the stakes are sufficiently high.

I think it's a non-sequitur, some might get more enjoyment out of tinkering with LLMs than out of whatever the assignment is asking you to do. But even if you don't believe that, it should be obvious that the ones using the tool needn't be the same as the ones putting in the work.