UA Polaris, like AC SS or SQ Business or TK Business lounges, are not *A lounges. So they don't need to admit other *A elites or apply unified standard. For UA/AC/SQ/TK, they provide alternative lounges for *G. Restriction for INTL J applies to distance/routes, so it excludes nearby carriers CM, AV, and UA short-haul.

So it depends whether or not the AC SFO MLL will be a *A lounge or not, they could call it SS or something else. I'm not sure what SQ labeled their lounge at SFO back in the days.