Its evaluation now purely relies on NNUE neural network.
So it's an good exmaple of the better lesson. More compute evently won against handwritten evaluation.
Stockfish developers thought old evaluation would help neural network so they kept the code for a few years, then it turned out that NNUE neural network didn't need any input of human chess knowledge.
AFAIK this is only a part of it, it still has its opening library, as well as the end-game one (IIRC chess is a solved game for up to seven remaining pieces on the board).
Also, the PR you link says the removed code in fact had a performance impact, just too low to justify its code size 25% of all Stockfish).
https://github.com/official-stockfish/Stockfish/pull/4674
Its evaluation now purely relies on NNUE neural network.
So it's an good exmaple of the better lesson. More compute evently won against handwritten evaluation. Stockfish developers thought old evaluation would help neural network so they kept the code for a few years, then it turned out that NNUE neural network didn't need any input of human chess knowledge.