Investing is game of information. If an investor can’t figure out who else will be on the cap table, they have much bigger problem.
The way it is going to go down is that investor during meeting will ask if founders think YC is in that round. If founders say something along the lines of YC decides after term sheet, it basically means no.
In the end , the overall result is that less YC companies will raise, but the good once still will, but it was always the case.