Except they did pick and choose SPCX and did special favors by giving them a multiplier on the float and an exceedingly short interval before including it in indices.
The only index that I know that float multiplied is Nasdaq which no one should even be investing in via their 401k anyway. Shitty index. Most consumers are utilizing some type of fund that tracks the CSRP, which float adjusts with no multiplier.
It's not even the Nasdaq Composite, It's the Nasdaq 100. And yes, the Nasdaq 100 is a shitty index because Nasdaq vs. NYSE is a bit of an arbitrary, tradition-based way to get tech exposure. It's missing NYSE tech companies (Oracle, Dell, Spotify, Uber) but gets some non-tech like Costco and Pepsi. It'd be like only dating iPhone users. It's sort of a rough proxy for something, but you're better off choosing what you actually care about.