I don't disagree with your point in general, but you're acting like leaving beer in primary is equivalent to adding something new to the fermenter. The yeast was there all along. It's still there when you move the beer to secondary, and it's there in the keg or bottle too, albeit in smaller quantities. Whatever flavors are imparted from the yeast are there regardless. Extra time spent on a large amount of yeast obviously intensifies certain flavors, but it's minimal, and those are not new flavors and not unusual flavors that don't belong in beer. Nobody is implying theres any supernatural suspension of flavor melding, just that it's not changing your beer into a different species, it's just a slightly different development and maturation of the already existing flavor profile.