Did you figure this one out? Sounds like you probably did.
I’ve been thinking about it again and how I would see the difference. I keep looking at the part of the Becoming definition that mentions achieving an identity with something and focusing on that as the difference. This works with Beast from Beauty and the Beast as one assumes he wasn’t going by ‘Beast’ prior to the transformation. Responding to the name Beast is one way of achieving that identity. And the ‘servants who aren’t serving’ are, I guess, losing their identities as servants and humans.
In most examples I can think of where a character gains or loses a physical attribute, their main concerns seem to lie somewhere in the area of “what’s happening to me?” Or “Who am I, and who am I becoming?” If your character is a regular guy that starts to see himself as a super human and becomes more heroic as he gets these super physical attributes, then I’d think he’s achieving an identity as a hero. But how does thinking of himself as a super human person cause conflict?
On the other side of it, I’m trying to think of a physical change that wouldn’t result in achieving an identity with that change. Maybe a boxer that already thinks of himself as the best fighter there is gaining an extra five pounds so he can fight in the heavyweight class? Someone who already feels like they could be a superhero growing wings and using them to try to save the day? Goku from Dragonball trying to obtain a certain strength level so he’ll stand a chance against Vegeeta? These characters might seem more concerned with ‘what’s happening to my body (as opposed to what’s happening to me)?’ Or ‘what (rather than who) am I and what am I becoming?’ Maybe ‘what do I need to gain or lose for my body to match who I am?’
That’s probably not right, but it does separate Becoming and Obtaining so that Becoming is clearly internal and Obtaining external.
If the character is definitely in Psychology, why wouldn’t Becoming be the true concern?