Not true in all cases. You have to test fit if you are not sure. I'm 5'10" with 30" inseam and fit in the King seat comfortably.
The only perceptible change (other than the increased comfort) is that I no longer can flat foot the bike while sitting. I am now touching the ground with the balls of my feet. But that is of no concern to me.
(The ball of the foot is the padded portion of the sole between the toes and the arch, underneath the heads of the metatarsal bones, on which the weight of the body rests when the heel is raised)