If you are talking about my ideas, my problem with starting from the bottom of the tree is that the tree is too big an complicated for a real game, and the details don't matter for a game. If you want perfection, I agree the only way is to start from the bottom and divide by 2 at a merge.
However, in a real game, approximations work very well (and miai counting can help justify this). The detail is how you approximate the count of followers without working them out perfectly. In a real game, since endgames are also fixed to space, moves tend to also crawl like a tree on the board (and that is only 2d not like infinity d possible for general endgames). Hence, the goal is to just say the top count is the average of the count of the two followers without doing much more calculation than that.
This is part of my idea behind
https://www.lifein19x19.com/viewtopic.p ... 60#p273160