Thanks for the replies!
The first EXP AAgent I spoke with was the one who informed me about the "airport control." She did manage to contact someone (placing me on hold) to get a window/aisle pair, but further back in the 2nd Y class cabin.
When I re-checked my seating assignment at aa.com and saw the seats were still displaying "unassigned," I called back to confirm that I still had the new, inferior seats as opposed to seats being truly unassigned.
At first, the second EXP agent couldn't see the new assignment, but after some digging around, found that indeed I did have the new seating assignment. As for regaining the original seats, that was a lost cause.
The second agent told me detailed information as to how many were on the UG list, how many open seats there were, what position I was in-- in the several years I've been EXP, I've never been given such detailed information!
Generally I'm told "well, there's a handful" or less than a "handful" (handful appears to be a common EXP unit of measure). When I've specifically asked what position I've been on the UG list, I've been told that they don't have access to that information, can't see, etc.
This experience is making me leery of future last minute seat changes because of the possibility that future seat changes may not be accepted due to Airport Control
vaporizing my original seat assignments and throwing me into an unassigned pool.
There should be a way when seats are under airport control one still retains the original seats, but just cannot switch to new seats.