Of course you can tell. If someone suddenly submits a mountainous pile of code out of nowhere that claims to fix every problem, you can make a reasonable estimate that the author used AI. It's then equally reasonable to suggest said author might not have taken the requisite time and detail to understand the scope of the problem.

This is the basis of the argument - it doesn't matter if you use AI or not, but it does matter if you know what you're doing or not.