The medical student culture at Yale is a bit different from that at other places, and I think they do take fit into account as a minor factor in admissions. But I'm sure every program thinks about 'fit' so it's hard to say that Yale is too different in that respect.
Smile, and for goodness' sake don't be overly tense or uptight. You're shopping for a car, and they're shopping for a driver, and ultimately it doesn't much matter whether you end up behind the wheel of a Bimmer or a Benz.