Thanks for your rudeness. Feel better now? Did I say I was in the business of fitting pro riders?

KOP is fine as a starting point, but nothing more. I'm not far off it - no more than 2cm back, but I also have a very short torso. Longer torsos are more common and a longer torso usually requires even more setback.

Find me a picture of a pro bike, particularly a euro pro, using a nonsetback post. Someone else tried a couple of months ago and failed. They found some straight posts, but the seat rail clamps were all set back. A true zero setback post has the center of the seatrail clamp over the centerline of the seat tube. It's far more common is see setback posts and the saddle slammed all the way back. If the frame brand happens to have a 72.5-73 degree STA, it's more likely that you might find an occasional nonsetback post, with the saddle all the way back.