That's true, but it's definitely not the case that nobody has accused Valve of being anticompetitive. They have a variety of plausibly anticompetitive practices and accusations.

It's also possible that some gamers did actually get money from Valve via arbitration, so they could've been found to have acted in an anticompetitive way, separately from the lawsuit. I've not been able to find anyone specifically saying that they did the arbitration, though.