I love how people have to obfuscate bike fit by using 'new' terms. Reach really isn't 'reach'. It's the front center distance from the bottom bracket to a perpendicular line from the middle of the steer tube. It's proportional to the top tube length but the top tube length is an easier measurement to make. "Reach", as most people would understand it and now called 'handlebar reach' to further obfuscate the issue, is the distance from the saddle to the handlebars which, unlike the top tube length, can be adjusted somewhat to fit individual tastes.

Stack height, which for years has been defined as the distance from the fork crown to the top of the steer tube, has now morphed into 'frame' stack height which is really just a gussied up version of the seattube length or the frame 'size' which is now a measure from the center of the bottom bracket to a virtual horizontal top tube along the seat tube. Yes, there will be a slight difference because one is vertical and one is measured at an angle but the difference isn't all that great and you can easily convert from one to the other or see that they are proportional to each other. A bike with a certain 'stack' isn't going to have a seat tube length that is radically different...at least not when measured to a virtual horizontal top tube.

From what I've observed lately in bicycle fit, it's appalling. I see far too many people who have been fitted to bikes that obviously don't fit them. I see lots of small people doing the Superman thing on bikes that are too big and I see far too many others who are riding bikes that make them look like they are trying to ride the bike their parents bought for them when they were 14. They look like BMX bikes with the rider folded in half between the saddle and the bars and the angle of their knees changes from 90 degrees to 85 degrees as they go from the top of the pedal stroke to the bottom.