Exactly.....it's an illusion many that many of us are after - discussion of extras, favourites, etc just destroy that.
I personally went with girls who had favourites that I seek, but if not all were forthcoming for whatever reason, then so be it - not going to cause tension by bringing it up. Just go with the flow. I've been lucky (or maybe just picking the right girls) in that only once or twice have I got 'not that baby', but done in a gentle way that kept things moving along. If anything it was more real!!