I asked about this in previous HN discussions. The old rule: You had to wait three months. Is there a meaningful economic difference between waiting 15 days or ~90 days? I don't see it. (For transparency: I own ETFs that track the S&P 500, which has lots of overlap with Nasdaq 100.) To be clear: OpenAI and Anthropic will sure IPO this year or next and have a similar effect -- they will be (or nearly) trillion dollar market caps upon listing.
If you short the company during the first 15 days, your short will get wiped out by the passive index buying. Nobody is going to short the stock to protect passive investors. The short will happen after the bag holders entered the market.
> SpaceX has successfully lobbied the Nasdaq stock exchange to loosen rules governing how and when it adds companies to its Nasdaq 100 index – a group of large-cap companies that it bills as “fundamentally sound and innovative.”