Those rules were implemented to protect the index from being skewed when an IPO happens because the IPO is exactly the moment where the stock may be overvalued and very volatile (compared to all the other stocks that are in the index). We especially don't know at IPO time if the company is changing the structure of the market because it's too soon. And in fact, we won't know for a couple more weeks or even years; but by that time the price will have stabilized.
The index is supposed to be slow at rebalancing to minimize costs and make it practical for providers as well.
And as I write this comment, I've just read that they cancelled the changes[1]. Which completely proves your last sentence wrong.
[1]: https://press.spglobal.com/2026-06-04-S-P-Dow-Jones-Indices-...