Apparently, because of refactoring done to support Strata, base materials are getting a massive increase in instruction count starting in UE 5.1: Shader Instructions 2-3 times more in 5.1.
The introduction of Strata is going to make engine modification more difficult, and if you’re modifying it around UE 5.1, you’re carrying over that performance bug from the refactoring.
Strata may be a net negative for NPR artists/developers using UE. Hopefully things change for the better soon? NPR is very popular in today’s digital entertainment industry, and to see UE struggling to offer support for it is very saddening.