T-SQL - OPTION (FAST x) and trace flag 8722
As far as I know, trace flags 8722, 8755, and 8602 were never officially documented. The last time I remember 8722 and 8755 being effective was in SQL Server 2000, so it is not surprising you find they are ignored in SQL Server 2012. Trace flag 8602 is still functional in SQL Server 2019 as a global or start-up flag to ignore index hints specifically.
For specific query patterns, it is often possible to remove the FAST n hint using plan guides. Even so, the best fix is to get the AX developers to fix it on the application side of things.