But it doesn't really matter except when the stock gets added to the index. The index funds and ETFs are going to rebalance their positions based on market cap and will not affect the price. These funds could affect the volatility though, since it's conceivable that with a lot of the shares locked up, these stocks are going to be more thinly traded than they would have otherwise been. This could create price instability, though I'm not sure there's any proof that it's true.

>...Unadjusted company market capitalizations of US$8.2 billion or more for the S&P 500..... are required.

[0] https://us.spindices.com/documents/methodologies/methodology...

It does matter when there are inflows, if there is new money coming into index funds all the stocks in the index benefit (they funds also sell all the stocks in the index when there are outflows). Non-indexed stock are less coupled to flows in and out of trackers.