Locatebiome command when used in nether incorrectly identifies chunks generated in 1.15

When I updated a backup of my world from 1.15 to 1.16 and used the locatebiome command to try to find a basalt delta, it brought me to chunks I had already generated, and that my F3 screen told was nether wastes

What I expected to happen was...:
The locatebiome command should locate a basalt delta, not what would be a basalt delta if I were to generate a new nether

What actually happened was...:
The command pointed me to nether wastes chunks that I had generated in 1.15

Steps to Reproduce:
1. Generate a world in 1.15 and go to the nether
2. Load enough nether chunks to hopefully generate what would be a new 1.16 biome
3. Update the world to release candidate 1
4. Use locatebiome command to try to find a new biome, and it might point you to already generated chunks that are nether wastes