I think the GA has to charge, but has some flexibility beyond that. On multi-l;egs, I've paid for E+ for one leg, been given it free for a second, or been switched to an exit row for the second
I was an AC-based *G the year they took free E+ away from non-UA elite's, and had GA's upgrade me to E+ for free at times. It just depends on who it is, so YMMV.