Originally Posted by Crescent Cycle

Fine. The number isn't the same, but when comparing different frame geometrties, if the ST intersects the BB, STA is actually more relevant than setback since the seatpost follows the seat tube angle, not the setback in mm. Setback in mm just helps people think in terms of reach and stack. In terms of actually deciding setback, STA is much more relevant because a saddle mounted the same way to the same seatpost will be in the same position relative to the BB once leg extension has been established. It doesn't matter if it is a 43cm ST with a little bit of addle setback or a 65cm ST with 50% more saddle setback. It's actually one of the more useless frame measures.

This is also the fit forum, and part of a relaxed geometry bike is allowing a relaxed fit. Just because the front end of a bike might be stable, if it has a 77 degree STA and an inherent 6 inches of saddle to bar drop for a given size, that doesn't make it a relaxed geometry. Don't try to imply that this is a ridiculous example either. Lots of small frames have very steep seat tubes, some exceeding 76, very stable front ends with 70 or less HTAs and lots of trail, and lots of people buy smaller frames to get lower stack heights. Just because the front end is "stable" doesn't mean they're relaxed geometries. Being able to get a relaxed fit is part of having a relaxed geometry.