I'm still very confused if it's just the game being very bad at generating stuff or if it's actually a bug, but if it isn't It would be still cool if a fix was possible in some kind.
I'm making a dimension mods needing nether generation and one my biome have a top layer of block x and a lower layer of block y, then the normal dimension block. I've sat that an ore should very frequently spawn in this biome, dimension and replacing the block x (top layer) with (amount of ore groups per chunk of 48). Right now, I've been searching since 30 minutes and I can't find any of this block on my top layer or it's waaay too rare. That's a huge problem as I need this type of mechanic.
Issue comments
Okay, so after an hour of testing intensely with try and error, I just understood why tf it wasn't working. My average number of ores in groups was one, which visibly made the ores just stop existing. Is there no way of making the ore only spawn as one ore per vein ?
(Generation wasn't working neither with smaller number of ore groups per chunk)