"Order (Triggering Progress Unit) to (Attack) to (Rally point of Triggering Unit)"
I've been looking for that, and I can't seem to find it. "Issue Order" doesn't seem to have the simple Attack, Attack-Move, or Move commands on it. That might have been updated in that last patch, but who knows.
As for why you wouldn't want it to be an Attack-Move rally point for a Move rally point its because of rushes. If its an Attack-Move rally point, and you're doing an early Zealot rush, if the enemy player sends out a probe to your Zealot rally point line, then he'll distract that Zealot and you might lose your rush. With a Move rally point that won't happen. Of course, if the enemy player has like 6 Stalkers on that rally point line, then you're still fucked.