(1.12.2)The biome will change if you re-create a biome specific customize world

Its a 1.12.2 bug and it is about custome world which is not a thing in 1.13. So its not really a important bug but I just want to point it out. If you re-create a biome specific world the biome will change to a diffrent one(the next one on the list) and if you re-create a mesa plateau biome the biome selector will show up as "?". I can't put my evidence video here because its to big, I'll upload it to youtube if you want a proof and the link is https://youtu.be/cq_ebcG-HqE