I remember seeing a video about this subject, since large IPOs are automatically included in index funds it is kinda of a way to extract value from passive investors. Insiders cash out before it hits the indexes, index crashes by a fraction for a %, all pensions in the country (and many overseas) pay for it.
But with OpenAI and SpaceX IPOing roughly at the same time it will likely be more than fraction of a % in this/next year.
but also, getting IPOs included captures the upside.
of course, public markets nowadays are definitely paying a pretty serious "agent-principal premium". (since public exits are usually very good for the C-suite and for all those vested stocks.)
so yeah, it seems it would make sense to buy the post-IPO dip, but then you would need to have some kind of formula for that, and ... that seems ripe for gaming by speculators ... so all in all, it's just more efficient to do what the rule of the index says. (and of course there's already speculation at the discontinuity.)
But with OpenAI and SpaceX IPOing roughly at the same time it will likely be more than fraction of a % in this/next year.