Dimension blacklist is unfortunately not doable for this type of feature, but the config does allow individual biomes. In which case, I recommend reaching out to the BYG devs to ensure their biomes are properly tagged as END in the biome dictionary so that this doesn't happen.

Can I get a log and copy of your config?

They also spawn in the End if there are modded biomes. Maybe there needs to be a dimension blacklist in addition to a biome blacklist?

log.zip