MSAR is for the AMCAS application service. This does not include all allopathic medical schools and has nothing to do with AAMC vs. AOA.
The Texas medical schools both allopathic and osteopathic are also completely separate. They use the TMDSAS application service.
When I applied for medical schools, I had to fill out 3 separate applications, including AMCAS, AACOMAS, and TMDSAS.