At least my index funds do that. They don't get to constantly trade like non-index funds do, and they typically stick with the index, but every index fund I own has a line about "we select stocks that we think will match the index", which is different from buying the stocks from the index.
Again, the vast majority of the time they are matching the index stocks. However they have the right.
Again, the vast majority of the time they are matching the index stocks. However they have the right.