dunno, it's certainly in how the saddle is designed, specialized alias and toupe are very flat, not extremely stiff or squishy for instance. For me, I think it's the width, flatness and hammock features that I like. cut out helped, but I had another specialized BG saddle that had no cut out, just indented and very flat that I could ride comfortably, can't remember the name, but it was all white.
Cannondale's saddle aren't any of these, but I could ride it without pain.
I should rephrase about bontrager saddles, I haven't ridden them, but search and you'll find enough posts that say the users felt painful sitting on them.

The saddles that I hated were too narrow, too much padding, too round or had too much gel in the wrong place. I have a set of sugoi shorts with thick gel which doesn't work at all for me, no matter which saddle I may be using. I think the thick gel in the wrong place is just one size too narrow for my sit bones, or I slip on the saddle changing the effective pressure points.

Interestingly, too wide doesn't seem to be a problem except when sitting far back on the saddle where I can feel the inner boney area start to knock/chafe the saddle