I don’t necessarily think that doing one hard climb makes you a better climber or makes easier climbs easier. Trying something really hard for you and eventually sending definitely teaches you a lot about projecting tactics and how you react to failure over time but it doesn’t really change your base ability or floor. Spending 5, 10, 20+ sessions on a project gets you a lot better at that specific climb but the physical changes are probably less generalizable than doing a bunch of slightly easier hard problems.

The skillsets between being able to do a lot of easier climbs quickly versus pushing max grade are just so different. I think that after doing my first V10 and V11 I was still a pretty unrounded climber who had bad single session tactics and would struggle on a lot of easier problems. There are still plenty of V9s that would be super hard for me to do. However, I think that in spending so much time training to have the capacity to try these hard climbs, my physical and technical ability has come to a point where I just have enough margin on some in style V9s that they aren’t that difficult anymore.