This. I would never move my boa in feed mode. She hits like a train and it's not worth risking a bite, for both our sakes. She has a ridiculous feeding response. I am aware that the OP is talking about a ball python, but I'm on the "feed in cage" side of the debate primarily for this reason.
Not sure what husbandry has to do with anything. How is it bad husbandry to not want to move a large constrictor that is still in feed mode?
It has nothing to do with being afraid. I don't want to move a large snake that thinks I'm food because it's not worth it. Bites from a large snake aren't particularly fun, and it's less stressful on her to avoid them as well. Fear has nothing to do with it, there's just no point. Just because I want to avoid a bite doesn't mean I'm going to dump my pets. That makes no sense.
Back to the main question.... OP - There's no real proof that feeding in the cage prevents cage aggression, so what you do is really up to you. About the only argument for it that I buy is that it prevents them from ingesting any substrate. Which honestly isn't really a big deal in most cases, but if that's something that concerns you you can lay down a plastic placemat over the loose substrate and still feed in the cage.
Basically for me it boils down to the fact that there are lots of reasons to not feed outside a cage.
-Risk finicky eaters being to nervous to eat in a less familiar place or after handling
-Risk moving a snake in feed mode (though bps are more laid back)
-Takes more time, you have to wait for them to fully eat before moving them back
-Risk stressing them upon moving them back