That is what people say! But since I've been recovering saddles I've learned that if I use the same leather on a B.72, and on a B.17 Standard, and on a Professional, and on a B.17 Narrow, the B.72 will be very soft, the B.17 Standard also pretty soft, the Professional a lot harder, and the Narrow very hard indeed. The width, not the thickness of the leather, determines the hardness.
That's really interesting data! The B17 Narrow is my favorite Brooks shape so far, and had assumed that Brooks has been using thinner leather on the B17 Standard specifically for those aforementioned newbies. I will correct my mental model.
While we're at it, do you suppose the width (and resulting flexibility) is why B72s are notorious for cracking around the nose?