Pathetic, but unsurprising.
As long as Riot (and when I say "Riot" I really mean their legal department and executive leadership) believes they can paper over this without a lawsuit, they will try to.
They were very obviously never going to allow their employees to eschew arbitration, they just wanted to prop up their "friendly neighborhood multinational corporation" image.
Regardless, it's time for their workforce to unionize. I'd love to see Riot trying to maintain their employee-friendly image while union-busting, I think they'd really have to just let it happen. I, for one, would happily support any such effort.
Maybe the workers could reach out to some of the higher-profile streamers/pros to endorse their efforts. Obviously many wouldn't be receptive, but I'd be shocked if they couldn't get a couple on their side, and that would skewer Riot's ability to control the narrative.
Anyway, keep your eyes on this situation, don't let them bundle it away as a temporary scandal. Let's make it clear that this attention is going to last until they demonstrate real change. I, for one, am not willing to support a company that mistreats their employees - I hadn't been playing for a few months anyway, but I pulled the trigger and uninstalled completely, and I won't even consider reinstalling until I'm convinced things have changed.