Ancient Cities are not entirely enclosed in the deep dark biome

[Hexze]

Ancient cities are not entirely covered in the deep dark biome. Instead of the entire area being contained in the deep dark biome, various surface biomes are interrupting the outer areas of the city. The center seems to generate correctly in each city I've found. Here you can clearly see the other biomes covering what is supposed to be the deep dark:

[astrsh]

Ancient city placement is delegated to vanilla to handle meaning there is no way of controlling where one might generate within a deep dark biome via Terra. The only solutution I can think of is increasing the size of deep dark patches to reduce the probability of this happening, which is controlled here https://github.com/PolyhedralDev/TerraOverworldConfig/blob/master/biome-providers/extrusions/add_deep_dark.yml#L7