Thank you for your post. I'm so glad that you're here wanting to support your partner in his treatment!
To answer your question though, it wouldn't be inappropriate but it probably wouldn't be helpful.
Whenever a Doctor or Psychologist is working with a client, they want to get to know them directly; build up a relationship, get an idea of where they're coming from and what they are struggling with and figure out how best to help them. To really do this, they need to do it 1:1.
If for example your letter said that your partner doesn't want to get out of bed, it would be inappropriate for the psychologist to use this with your partner. Not only does it completely put him on the spot, but it removes all that opportunity to build up trust and figure out the context of what's really going on.
I hope this answers your question!