Single biome world gen error

Single biome world generation doesn't generate the correct biome.

What I expected to happen was...:
Expected a Warped Woods biome in the Overworld

What actually happened was...:
A world of plain grass blocks and lakes generated along with Bastion structures... but no Warped Woods? No fungi, no vines, no nylium... just dirt! Oh, and particles, with Warped ambience.

Steps to Reproduce:
1. Make a new, single biome world and customize with Warped Woods!