Some companies, mine included, BAN photography on the flight deck at any time. Any breech of this policy could , and has in the past, result in disciplinary action even termination!
Don't know RYR's policy, but this could be the Captain's reason.
I don't believe RYR have such a draconian policy. I tend to think that the Captain simply didn't want to be part of the photo, or was in fact assisting the OP in making what was essentially a FD photo even better (without pilots obstructing any of the instrumentation. Btw Jn14:6, your company must be fun to work for!