I've had many (probably 100) red eye domestic to later than 6am international flight where I've always been given lounge access at the first point of check-in. I'm always given lounge access on arriving next day from an international to domestic connection. I think they key is to have an international segment that does not include a stop over. The 6am rule is not referenced for elite members but for J/F.
https://www.aa.com/i18n/travel-info/...nge-access.jsp
oneworld Emerald and Sapphire customers
If you’re departing on a flight marketed and operated by a oneworld carrier, regardless of your class of service, you may enjoy:
First and Business Class customers
Lounge access is not available if you’re traveling on American Airlines solely within the United States or between the United States and the Caribbean, Canada, or Mexico (except Mexico City).
Your access is determined by showing your boarding pass departing on an international flight marketed and operated by a oneworld carrier that is five hours or longer, or connecting to one on the same day or before 6 a.m. the following day. You may enjoy access to:
Telling elite AA members they don't have access when in practice and AA rules they do is misleading and inaccurate.
Wanderlust is taking rules from a OW site and applying them inappropriately to a AA EXP accessing an AA lounge. AA rules apply in this case and AA EXP and Plt on a qualifying international flight have access. 5 hours flights and 6am departure have no applicability here.