It has happened to me! Though only domestically. Twice. Both times were when traveling as a pair and seated in the 2-seat sides of 767s. The GA had parties of two without seats, and found me (1P) and Mrs. PVDProf (no status) and put us next to each other in C or F. One time we were on separate PNRs. It probably helped that we have the same surname, so the GA could tell we were together.

Told the GA, "Thanks for upgrading both of us, because if you only did one, you know who'd be sitting in the back!"