I could rate any game I wanted from start.
Anyway, I generally use "submissions in need of rating" to rate games with fewer votes.
However, if I was forced to rate a game with only a Windows image at start, I would be annoyed : first, I don't have Windows, some prototypes run with wine, some don't, and second, I don't really like to be forced to run a program made by an anonymous person on my machine.