Harder here doesn’t mean slower. Reading and understanding your own code is way faster than writing and testing it, but it’s not easy.

AI tools don’t prevent people from understanding the code they are producing as it wouldn’t actually take that much time, but there’s a natural tendency to avoid hard work. Of course AI code is generally terrible making the process even more painful, but you where just looking at the context that created it so you have a leg up.

Certainly AI tools don't prevent anything per se, that's management's job. Deadlines and other forms of time pressure being what they are it's trivial to construct a narrative where developers are producing (and shipping) code significantly faster than the resulting codebase can be fully comprehended.