Even after applying for AOS, if you still have a dual intent visa (H1 or similar visa) stamped and valid, then you can use that to travel.
You are not mandated to get AP in that case.
When you do not have a valid visa and you go for EAD for your work, your travel needs AP.
H1 and similar visas are dual intent (you can work & travel).
EAD is only for work. So you need AP for travel.
Guess, I am right...guys, correct me if not.