We're not takling about a 110 km vs a 230 km stage, but i.e. 180 km vs 230 km. Even in those marathon mountain stages in the past the extra length was mostly flat and/or they often had a higher percentage of climbing on lower gradients. I really don't see why that is better than the Pla d'Adet stage above or the Joux Plane stage I mentioned. It's not like we've ever seen something like St.Girons to Luz Ardiden via Portet d'Aspet, Mente, Portillon, Peyresourde, Azet, Ancizan and Tourmalet (which would be about 220 km and a shitload of climing above 7 %).Of course there is. You might as well argue that Paris-Roubaix don't need the first 100 km, as the last 160 km are so well designed.
Stages also have impacts that last longer than to their finish line. The day after a marathons is different to a day after a simple VO2 Max effort.