Maybe I’m misunderstanding this entirely. The way I’m used to you have a listing for any seat on the plane, all by seniority order. As a last resort, if the cabin is full, the jumpseat(s) get assigned, again in order of seniority (to people eligible for it). I’ve never heard of people being allowed to double list out of order etc. (and the carriers I’ve worked at are ALPA too) where I am from that’s frowned upon because you block several seats without ever actually using them.
If that’s possible at UA I can get his patronizing stance. He knew he was gonna get a seat in the back and was now offering his Jumpseat to me (even though it’s not even him deciding who gets it ultimately). Yes people can argue that he was doing me a solid, however imho it’s not the way it’s supposed to be. If you get a seat in the cabin you should take it and not mess up the system by listing for the JS only to give it to someone else at the last minute to stand there as a star.