OK, let's be hypothetical.

You have 3 riders of identical height.

One conforms to the expected body proportions. We'll call him Norm.
One has longer legs, and shorter torso. We'll call him Flo Mingo.
One has shorter legs and longer torso. We'll call him Chip Pantsy.

When Trecalized designs a bike, they design it for Norm. His leg length defines the seat height for that model, and its distance behind the BB. If they target his back angle to be 45°, his shoulder will fall .707 forward and above the saddle, and his arms will describe an arc around that shoulder that meets the hoods somewhere below saddle height. Frame is designed with stack and reach to place the bars on this arc. Call this the Norm arc.

So now Flo tries the bike. With longer legs, the saddle moves up and back, on an angle slacker than STA, generally. Compounding this movement, Flo's torso is shorter, so his .707T is lower, and farther back from the bars than Norm's, provided he tries for the same 45° back angle. His shoulder pivot point is now much different than Norm's, definitely closer to the BB, and most likely higher. Evn if Flo's arm length matches Norm's, the Flo arc has moved NW, or into quadrant II, from Norm, so his target stack and reach numbers to hit the Flo arc, will need to be shorter and taller to hit. Hence, endurance geometry, or since frames get taller quicker than longer, he sizes up to hit the arc.

Chip has the opposite issue. Seat is now lower and forward of Norm, his long torso puts his shoulder pivot more forward and higher, so his target curve of hand position has moved SE, or into quadrant IV. So Chip wants the shortest stack or longest reach he can get. Sizing up screws him, so he either goes crazy long flipped down stem, or sizes down to pick up every chance to hit the curve.

Both Flo and Chip can ride Norm's bike with no changes by changing their back angle. Flo will set his seat position, and then stretch to reach the bars. Chip will set his seat, and sit bolt upright.

I am a Chip, compounded by very long arms. When I used CC's frame size calculator, it told me to look for a 690 eff TT, coupled with a 180mm stem. By riding a 58, and lots of drop, I hit my ideal arc with production components.