Cool piece. I think there's a difference between growing/picking up skills and mastering them though that isn't covered. For instance, with aesthetic skills (drawing, sketching), I think you need to have some degree of innate creativity, or an eye, to truly become a master. It's the reason why only a few students that were apprentices to the Great Renaissance Painters went on to become famous artists themselves. There were many, many artists in the bottegas of Da Vinci or Rubens who were able to copy and distribute works like those artists, but never paint masterpieces. (
https://www.artspace.com/magazine/art_101/art_market/the-evo...)
It's just one example, but I think there a lot of other principles that become a part of "Skill Trees," including collaboration, the environment you're learning in, and maybe an element of innate talent that means you never have to break down the skill.