You can't possibly know that. Professional cyclists with thousands of miles under their road shoes can't really tell what their bodies are doing without video cameras and tape measures and laser levels, etc. By the seat of the cycling shorts assumptions is what ****'s up cyclists knees and other parts of their anatomy. I wouldn't even trust most cyclists to know if they were falling forward or not when they let go of the bars. The plumb bob from the front of the knee is an objective, repeatable measurement that can give a whole lot of information as to fit along with measuring particulars of a given cyclist and matching that with measurements of particulars of the bike they are riding. Nor am I a slave to numbers, once the facts are in, I can and do vary things a little more here a little less there and aim for long term comfort and performance with the numbers as a baseline for comparison.

H

P.S. It would be harder to "slip forward" on the saddle if it was pitched nose up a bit or at least dead level. Just saying.