I'm sure it's in their contract with PP as well that they can prioritize who they allow in.

Before the skyclub had Kahlua as a comped alcohol, I would use the Club at ATL if I had an international layover at ATL and there were two times I left when the crowd was busy and they weren't allowing PP swipes in, only their airline partners who had an eligible ticket they partnered with. At the PP lounge at Lima the last two times I flew back (before covid) they had a separate line for airline passengers who had access and a different line for priority pass customers. They were allowing PP in but they would allow like six airlline passengers in as people were leaving for every two PP members and the airline line was a lot shorter.

When the VS lounge was in the same terminal as Delta for a while at LAX and Virgin was a part of PP, they were only allowing PP swipes in until like noon in the Virgin lounge. And they didn't have that great of a selection. They only had a couple beers and wine and packaged snacks and the dragon told me they opened up the bar and put out the hot food once the lounge was open for their passengers.

I haven't encountered this but I'm told when an Am Ex lounge is at capacity some lounges will give priority to Centurion card holders over Delta Reserve and Platinum cardholders.

I'd rather deal with the restrictions and have access than have no access at all. You know Virgin and BA are going to take care of their passengers spending thousrands on a business class or first class ticket over a priority pass or Am Ex swipe.