Even though the behavior of walls on flat ground is indeed weird, I'm not sure if we want to change any wall or pd hitboxes.
The reason is quite simple: As Tagada correctly states, on most maps walls do their job very well now.
I haven't tested them all, but It's only only the perfectly flat maps that the weird behavior of highly deterministic, range dependent behavior seems to take place.
Super flat maps are really artificial anyway, so I'm not sure if it's a problem that the wall+pd behavior is also weird.