In my experience, the AA EXP desk won't touch a RTW reservation - they'll (politely) make you call the RTW desk (tomorrow, if they are not open). They're smart enough to know that RTW tickets have 'complicated' rules and they readily admit that they may not know all the issues. I guess regular reservations aren't as wise and, for my part, it wouldn't even occur to me to try to get regular AA reservations to touch a RTW ticket - that's why there's a specialist RTW desk. The fact that you spent 15 minutes arguing says it all - after 1 minute arguing, I would have simply said "Thanks, I'll call the RTW desk tomorrow" and hung up.
But the problem is when you need to make a last minute change and the RTW desk is not open. Then you will have to use the reservations team. From my experience before on all other airlines, their reservations staff can perform simple date/time changes with minimal hassle. I mean the fare rules are quite simple for these changes. No reissue, just revalidate - cancel booking and create booking. No need to add fees/charges/taxes etc... Just have to make sure you get the O and X correct.
From now on I will avoid where possible to deal with AA reservations on XONEX products.