I've never had a therapist ask to see my wounds, I find that really odd and kinda crossing a boundary. There's no reason that I can see why a therapist should put their client through that. I'm sorry they made you feel so uncomfortable. Can you tell them next time you see that that was crossing a line for you or ask for clarification why they felt it was necessary?
Nurses/doctors on the other hand are a little different. I'm fine with showing them because they're MEDICAL personnel.