I'm making a data pack that extends the Nether terrain up to the would build limit, however, I have encountered a problem with surface builders.

nether_forest, soul_sand_valley and basalt_deltas surface builders are capped at y=127 and not generating nylium, soul sand/soil, and basalt/blackstone patches respectively above that height.

It presumably is done on purpose as normal nether terrain generator has a height of 128, meaning covering anything above that height has no purpose, as there is no terrain. Nowever, customized worlds that exceed this height suffer from this limitation.

Considering the fact all other surface builders, for example shattered_savanna or giant_tree_taiga have no issue covering blocks above y=127 with grass/dirt, I would suggest raising that limit for nether surface builders to y=255 or unlimited (depending on hot other builders are coded).

Attached the data pack demonstrating the issue.

Note: I can't currently make a custom surface builder based on default that places nylium blocks, as custom surfce builders appear to be not working in this snapshot.