There are only 8 tables in the dining room with a maximum capacity of 16.
UA839 and 98 leave at about the same time in the evening, with 98 Polaris seats just with those 2 flights. So even if just 10% of the eligible passengers wanted to dine, there wouldn't be enough room. Add in other Polaris seats and any other eligible passengers (who may opt to connect onward on UA metal and not use the *A lounge) and there's no room for them to eat.
When the circular area was closed off during construction, I thought they'd expand into that entire space. I was surprised to see if left open.
Prior to 4pm yesterday, crowds were light into the club; so much so that UA invited LAX-area elites in for free. Even at its busiest, I never counted more than 25 "passengers" trying out the lounge at once. Now I know not every J passenger uses a lounge and not everyone that uses the lounge will eat dinner, but I think space will still become an issue here, especially if you have 2+ Polaris flights leaving at about the same time.