In any case, one of my points is, say you want a fund that tracks the stock market, a Vanguard index fund maybe, and you are concerned about their S&P 500 fund being gamed or "front-run" or whatever you want to call it. You don't trust it. They have a "total market" fund with the same 0.03% expenses. Plus, the AUM are the same or a little more, so you don't even have to go against the herd. So if something did happen to the S&P 500 fund, it seems like it would be inconsequential. Who needs it? And people are going to notice if something is wrong because the differences between the S&P 500 fund and the S&P 500 index, or between the fund and the total market, are so small.
What you need to worry about is some obscure index fund where everybody is not aware of what it should return. Like, I don't know, USO?