The M5 isn't a radical redesign over the M4 nor are the Pro / Max versions of the M3 / M4 significantly different than their corresponding base chips. Apple was able to release M3 / M4 base, Pro, and Max at the same time. Why not the M5 versions?The rumor mill is pretty solid on this one. M6 Pro/Max will get the redesign (about a year away). M5 launched on its own because they had that chip ready, and the M5 Pro/Max needed more time.
My thought is Apple is holding something back whether it be the Pro / Max chips themselves, form factor, screen, something else. But I am speculating just like everyone else. As I said Apple does what Apple does regardless if it makes sense to any of us.