A data point on my experience.
Booked AS metal using AA award miles.
Had to call AS, a long 30 minute convo to add my AA FFP# and EXP status.
After AA FFP# was in my AS account, I was able to select seat (section allocated for ow elites).
at T24 (Not entirely sure), both I & wife were UG'd to F without my knowing. Sweet!
OTH, tried to do exactly the same thing with BA. After a 25 minute call, agent was unable to even verify who I am. She kept on going in circle asking all the "security" questions. To no avail, I hung up.
Here begs a question: Why can't this kind of simple thing be done online, even after ticket has been issued?