I don't think that's what he meant. In GT5 under practice you could select one-make race and it would fill the grid with whatever model you were driving, so you could have a one-make race with any car in the game. I used this feature sometimes to get photos for my spec one-make racing threads and I'm disappointed it is gone. The only one-make races in GT6 so far are the ones where they choose a car for you so they are extremely limited compared to GT5.