[dgacmu]

Vanguard's AUM grew by about 1 trillion last year. This hypothetical 100M is 1/3rd of a day of that - and one almost certainly doesn't move all of it in a single day. Nor is one likely to keep all of it in a single fund. Once you have a bog-standard stocks/bonds/cash/maybe RE split, 100M isn't moving the market. I think you're off by an order of magnitude.

Where you're right, of course, is that 100M justifies considerably greater attention to the money management. But the biggest focus is tax efficiency, not the micro details of the market.