It's completely hospital dependent which in turn is dictated by the DPM who heads the department. Large institutions and corporations tend to only accept ABFAS for a surgical pod but will accept ABPM for non surgical pods. Both boards now require you pass within a certain time frame after residency. If not, you can never sit for them again. ABPM is easy peasy, ABFAS is a complete circus, so I would sit for both if you can just in case.
I have a friend who thought they could get ABFAS no problem, did not take the ABPM at all and did not attempt ABFAS until the 6th year out of residency. They failed once already. Turns out its not so easy and now they only have 1 chance left to pass ABFAS AND can no longer sit for ABPM. If they don't pass ABFAS this next round, they're SOL.