IMO GS/1K/MM should get Polaris lounge access when traveling on an international tix even in Y!
Polaris doesn't have the capacity and wasn't designed to accommodate GS and 1K flying in Y. If anything, I think Polaris was too generous to allow *A J/F passengers, but I guess that's a compromise for swallowing up BR/SQ lounges in SFO. Other airports will probably be less affected as other *A carriers mostly depart out of other terminals.
Polaris lounge access is probably a good middle ground between AC Signature Suite and AA Flagship which was designed to accommodate OW J and OWE, hence why there's no sit-down service.and much larger in size.