I’m no lawyer, but in order for the ex parte argument to hold water in this case, the court case would have to have been discussed. A traditional meeting of justices and presidents elect (both reagan and clinton did this, gw deferred)is what went on here.
The notion that Scalia and Thomas would be parties to an ex parte decision defies common sense. JMO.
The notion that Scalia and Thomas met ex parte is supported by the photographic evidence.
Did Reagan and Clinton have cases pending before the SCOTUS at the time of the meetings you cite?