Well this is a long story.

Booked an open jaw TATL, A - B and C - D; A - B is in N (discounted Y) while C - D is in W (full fare premium econ). No EF used this time.
Called EXP, A - B waitlisted for SWU, but C - D, I specifically asked for miles and copay upgrade (which for W, has no copay requirement; Returning city "C" is not in the UK so no tax implications here)

1st EXP Agent: "Sir you need $350 copay." Told him about W copay rules, he went back and said my miles upgrade has been requested;
2nd EXP Agent: "Sir you need $350 copay." Told her about W copay rules, she went back and said my miles upgrade has been requested;

Today, T - 17 days, online booking showed "your trip details can't be displayed". I suspected one of the upgrade might be cleared, so I called EXP desk and played dumb ("what's going on here?")

3rd EXP Agent: "Sir your SWU has been cleared on the inbound leg". Me: "...." Going through the same W copay rules, this EXP agent obviously knew what I was talking about and spent about 15 mins to re-ticket. Gave her an above and beyond ticket at the end of the call.

Lessons:
1. EXP agents vary - especially with new concept like PEY;
2. Never take EXP agents too seriously...
3. T - 17 days, I guess I can't complain huh?

Next step:
AA posts the wrong EQM for the PEY leg, I call back for a 4th EXP Agent and spend another 30 minutes figuring EQM out.