Deep buttoning in leather is a different job from deep buttoning in cloth, and the difference is that leather will not be talked into anything.
Woven fabric has give. Pull a button and the cloth around it stretches slightly in every direction, so small errors in the layout absorb themselves and the pleats between buttons settle where they want to. Leather has almost none of that - it is a skin, not a weave, and it will not ease. Whatever fullness is not planned for has nowhere to go, and it shows up as a hard crease running off at an angle from a button.
So on a leather back the fullness is calculated for each diamond before any hole is made, and the hide is cut oversize by exactly that amount. Each button is pulled in sequence, and as it is pulled the upholsterer folds the pleat by hand and sets it down with a smooth bone-ended tool, deciding where that fold will lie rather than letting the material decide.
Every pleat on this back was placed deliberately, one at a time. That is why they all run the same way and meet at the same angle - something leather never does on its own.