My take is that if only one of the fifteen airlines makes this interpretation it is likely not the correct one.
My take is also that turning an exception into a 24/7-rule to deny entry to oneworld members in certain lounges, not even hiding behind "peak hours" or "lounge full" but clearly stating the lounge is simply not accessible to oneworld members at all, it is a behaviour that justifies strong and repeated criticism.
I am not blaming you, but I found your take a bit odd. You say we should not claim they are breaking the rules? Sure, no one of us can prove they break the rules as we don't have access to the legal papers. But it is pretty clear there is a deliberate and continuos breach of the spirit of the alliance. I am sorry, but I can't sit quietly and watch that, even if there technically might exist a loophole.
If Finnair marketed "Tickets to JFK now only 1€ r/t" and it turned out they did publish such a fare but never released any availability to the fare bucket on any flight. Would that be a justifiable behaviour if they simply add a fine print "some departures to JFK can be busy and the number of seats might be restricted during peak periods"?