Here's a spanner in the works. Before I was Elite (when I was KC Silver) I was gifted 2x upgrades by an Elite for 2x separate flights. Both these upgrades cleared at T-7 while my Gold colleague (on a different PNR, same booking class) had to wait till check-in. I've heard a few anecdotes similar so I've always figured that upgrades gifted by an Elite cleared after Elites but before Gold.