Sorry to bump this older post, but it seem directly relevant to the issue I’m facing - and I’m just seeking confirmation as to if my thinking is correct (and if it is, clearing up the issue for others as well).
I’ve run into an issue with the AMS2 on P1S whereby if there is only one filament defined on the prepare tab, even though it was configured at time of sending the file to the printer (send, as in to the sd card via LAN, not print via cloud) to use the ABS in slot 4 of the AMS it will use slot 1, which is PLA … 
I baby sat the printer and caught it in the act of misloading as I suspected it was loading the wrong slots after some queued PLA prints came out in the … wrong colours 
I then re-loaded the project, inserted filaments 1-3, and configured it to use filament 4 as the active one for the print (again, slot 4 ABS) and now the printer correctly used that slot when loaded from the sd card. It seems to me that when loading a print from the SD card that the P1/AMS2 will blindly/dumbly just use the filaments as sequenced in the prepare → project filaments section, regardless of the type. i.e. I think the “mapping” part that is mentioned here (although in relation to the X1) only works on the P1 if you printing directly via Bambu Studio or Bambu Handy app… which unfortunately makes my P1S way, way, way dumber than my A1 
I mean, seriously… the printer didn’t even baulk at using PLA when the print job asked for ABS… what is the point of having RFID reels? 
That part I really am surprised at.