Legacy loot mounts

So I’m returning from break and haven’t played since early Legion. I’ve read up on some of the loot mode change stuff but can’t find an answer for my situation.

I have a RAF and I’m trying to show him old raid content as he gets levels for it. He wants to see Firelands but if I run that with him when he gets to 85… and the mount I don’t have drops, can he potentially have the mount go to him and not be able to trade it to me? I took him into Obsidian Sanctum to get that mount for him when he got 80 but the mount went to me, even though I’ve had it already, and I can’t trade it to him.