Maybe, most indexes do not have to follow the index. they just need to match the returns. An index fund manager has choice of what stocks to buy. However an index fund doesn't have enough managers to make many choices and so they normally buy just what is in the index. However all index fund managers know they are large enough that if they change their holdings "instantly" when the index it self changes the market will collapse and so the fund will under perform. Thus index fund managers are always trying to figure out what the index will do so they can start buying/selling stocks in smaller amounts before the change happens.
How each fund handles this is up to the managers. (and "total market" funds have less ability and need to do this)
Just look up the performance of Mutual Funds vs S&P500.
Again, the vast majority of the time they are matching the index stocks. However they have the right.
Typically managers pay is such that they don't get awards for guessing correctly, so they won't get any upside from a correct second guess, and they will see downsides from incorrect guesses.
Also unlike traditional funds, there are not enough managers to follow every company, so they can't pick stocks that will win just because they don't have enough to time research the stock. When they pick a stock they are just looking at the high level will this company perform like the other peers in the industry long term.
On the other hand, do you want to be the one who says, "As a rule we follow the index, but this time we decided to break our own rule, and as a result we lost X% of returns"?
Better wrong with everybody else than wrong on my own.
Changing one of those features undermines the reasons for including the index. Doing it specifically for the purpose of including a firm where large pension funds have also been extraordinarily critical of the governance structure as a particular source of risk [0] even moreso.
[0] https://www.reuters.com/legal/government/new-york-california...
Right, if they've advertised as an S&P 500 index fund, they have to robotically follow the S&P 500, stupid inclusions and all. Changing that strategy would require ... a lengthy process involving input from shareholders.
However, someone can still start e.g. a "classic S&P 500" fund that follows the old rules for inclusion, and I suspect we'll see that in response to these recent decision.