I think you mean FAA and not the FCC!
Also, FWIW, the EC has voted to change the wording of the infamous comma sentence. Here is the new wording:
To clarify the actual intent, GENERAL, item 2.(c) was rewritten to read: When within three (3) miles of an airport, notify the airport authority and air traffic control (ATC) where applicable, and will not fly higher than approximately 400 feet above ground level unless otherwise agreed upon by the airport authority and/or ATC (where applicable).
With regard to AC 91-57, recognize what the legal definition in the sense they are using it os "authority". AC 91-57 is still a Guidance and they say as much. They say follow the guidence of AC 91-57. They do not say "comply" with it. Careful legalese to be sure. They know that the AC carries no force of law.
But they are clearly drawing the line with regard to commercial non-hobbyist uses.