I've been told by helpful agents (as well as knowledgeable flyertalkers) that (before DM) there are 3 levels of waitlist for upgrade: PA, PB, and PD. Usually, PA is for UGS and 1K (as well as anybody using SWU), PB for 1P and 2P using miles, and PD for general members. Therefore, changing status from 2P to 1P does not help, while becoming 1K does.

Please someone correct me if I'm mistaken.

On the other hand, of course, some agents make exceptions or mistakes from time to time - either nice or bad!