You're right I shouldn't make a blanket statement - all the drafts I get are ruined by them, but that's probably why they're in the auctions. But they're also the leading producers of puppy mills which makes me pretty ticked.
Anyway I rant ^^
Yes, teaching them to yield their hind end is very important, especially when they have issues like that - I personally teach my horses to yield every part of their body to maintain proper personal space. Good luck!