1.16.4, 20w49a, 20w51a, 1.16.5, 21w06a, 21w08b, 21w10a, 21w16a, 21w18a, 1.17.1
Several Hills biomes do not generate sporadically replacing patches of their regular biome counterparts. They generate like a completely separate large patch biomes, making them quite rare.
Taiga generates small patches of its hills biome.
But - Swamp doesn't.
Affected Biomes: (May be incomplete)
- Dark Forest Hills
- Tall Birch Hills
- Giant Spruce Taiga Hills
- Swamp Hills