I’m not the best person to ask about this; I read about this mostly because of the recent rule changes. I have seen a number of financial publications writing articles about it, though.

MSCI

I did read one article commenting that MSCI has not changed their rules and has less-permissive inclusion rules. If you have a lot of money on the line, though, I would not take my own understanding as being authoritative (I mean, even aside from the general principle of taking statements from random unknown names on the Internet with a grain of salt; I’m explicitly not claiming to have a lot of domain expertise here).

I think that the question is why some of the indices decided to change their rules, and whether the same logic might apply to other index operators, and I don’t know the answer to that. I’ve certainly seen many outraged people on Reddit saying that the driving factor is clearly some form of corrupt influence from company that might list on the index operator. An index operator might simply be concerned about keeping their index a useful metric that reflects market behavior — huge IPOs are market behavior. shrugs I don’t have the knowledge to say what’s a reasonable conclusion there, though I think that concern about misincentives is fair.

I do think that it might be worth looking into if it’s something that affects you, though. There are financial publications that have people writing about this, if you want to go digging up articles on it.

Indices that don’t include spacex can still be affected. As the major indices have to make liquidity available to purchase SPCX, that will suppress the value of everything else in their baskets to some extent. So the indices not including SPCX may be immune to direct SPCX volatility, but they won’t be immune to all the effects of rapid inclusion.