They don't even get to actually opt out, just "for individual sexual harassment and sexual assault claims"; the qualifier "individual" is probably doing a lot of heavy lifting too.

My sense is that Riot executive are supportive of making a change. Legal, on the other hand, might not want to restart arbitrations and rewrite contracts.

I’m struggling to think of other white collar jobs that have unionized; at least in the US. Examples?

I know more than one person in tech who is deeply skeptical of the idea of unionization. I'll go with my concerns. Among other things, unions are sometimes known to do things like prize seniority and standardize entry requirements across an entire sector. Which is to say entrench credentialism and ageism. I don't want to see all my self-taught colleagues thrown out, or the ladder pulled up behind them. And in a sector that already has ageism problems, I don't see how writing it down will make it better.

Sometimes I hear "It doesn't have to be that way!" from unionization supporters. I have no doubt that they are correct - no union has to turn out that way. This possibility gives me little assurance.

Further, most of the time pitches come in the form of "Don't you care about privacy? Join the union and together we can!". Which often comes across as someone looking for tech money to fund their advocacy rather than genuinely trying to improve the working condititons of people in tech.