I've had miles that posted to BA removed and then successfully applied for credit with AA. [I've had to do this alot and sometimes do it for purposes of managing my BA status qualification/requalification. ]

And miles can credit to the wrong program no matter what the BA or AA boarding pass says. For some reason, if BA touches my boarding passes, it's far more likely that "anything" can happen in terms of where the miles do or do not go.

What's printed (or not printed) on the boarding pass has not been a guarantee that the miles credit correctly (or don't credit per my desired account/timing).

These issues are not unique to AA/OneWorld. I've had similarly bizarre issues when flying NW & KLM and crediting my DL or NW accounts. [I don't seem to have this issue with Star Alliance carriers and crediting my UA or other accounts.]