huh? popping off an edge is a prereq for just about any rotation past 180. Popping off an edge shouldn't throw you off balance.
Obviously we have a disconnect. The OP is specifically asking about straight airs, not rotation, that would be a whole other conversation.
For straight airs I would never ever teach a new rider to favor any edge.
AASI teaches to pop from a flat base
Snowboard addiction teaches to pop from a flat base
Jumping with Jussie teaches to pop from a flat base
I could make this list very long but I'll stop there. The main point is if your teaching a new rider to jump you should be teaching them the safest most effective way, which is off a flat base.
I can pop off my heels and toes and do a nice straight air, but I'm an experienced rider and I would never teach these methods.