Given that "detaching" costs a specific command, but A-ttaching happens by just stopping in the hex, I can see why the rules would work differently there.
And I think a leader can certainly enter a hex with a square in it and, if he does not move further, he would be "attached." He may leader retreat through a square and attach or (if he has movement remaining) continue to retreat out of it.
Yep, that makes sense. As always, it's best to not over think it and look for something that isn't there. Thanks for the input.