United would do this to combat the pressure in the PS market. American offer flagship lounges, JetBlue offers a far superior product, delta offers superior skyclubs. Offering Polaris lounges will give them a step up. Secondly the GS access on international flights will be very limited because not that many GS fly internationally in coach. This benefit will be nice but will not change the way a GS buys tickets. However it will also allow a very valuable customer to access Polaris lounges when their not experiencing Polaris. It keeps the customer very happy. Just like when a OWE access qantas or CX first on a cheap economy ticket.