There is a lot of misunderstanding of OMB.119 here.
It is a stretch for the FAA to apply it to safety regulations, it is for production and manufacturing standards
Nothing the AMA currently has or does meets the requirements for use by a Federal Agency.
External standards, if adopted, are applied to everyone not the group that developed them.
The organization that provides the standards reliinquishes rights and control over their standards.
The organization that provided the standard can not make futher changes to their standards except to make them stricter than the Govt accepted standard.
Read it
HERE