Most OpUps are done ~1 hour before departure when the # of check-ins is becoming clear and seats need to be freed up to accommodate everybody. Sure, you could run into the Polaris Lounge for a quick bite but usually not long enough for the restaurant.

I'm OK with United removing access to the Polaris Lounge in this situation. Keeps the crowding down. And maybe United has finally realized they built a product that people are clamoring for (Prem Plus) and they consistently oversell that cabin. Margins must be good enough for United to continue to do this. So they OpUp more people and prevent PL access.

The flyer used no currency (cash, PlusPoints) to get the Polaris seat so they shouldn't be entitled to the benefits (free SDC to the same cabin, for example). BTW, I also expect that if you are the lucky recipient of an OpUp before check-in that your baggage allowance is tied to your booked cabin / status.

-RM