User blog comment:Gen. Grievous1138/On the new biomes/@comment-25101089-20151212220148/@comment-25869554-20151213154556

I think it should be judged by the code, which, after all, is what makes the mod. In the code, the East Bight and the Long Marshes both 'extend' the code for Wilderland, but the Field of Celebrant 'extends' the general Biome code, making it a biome in its own right.