As a non-climber, when I watch the Dawn Wall videos, there's an illusion that the surface is 90 degrees sheer, perpendicular to the ground. Understanding that there is actually a slight incline puts those tiny holds in a little more context, moving the concept of clinging to the wall's surface from "impossible" to "outrageous".

For some comparison here's Adam Ondra climbing another route. And no, this photo wasn't rotated 90°, it is really an overhang :)

https://www.8a.nu/images/news/large/636002137114161240_13320...

A famous bouldering problem, "Witlness the Fitness" that inclues a cieling:

https://www.youtube.com/watch?v=_PP1AK1Aqis

The thing is, usually those foot holds are holding most of the weight - a chip for the foot is worth a jug in the hand :)

Not to mention core strength! Tiny little holds are often at inconvenient angles. To pull on those features his entire body is engaged.