surface biome bleed underground

every time you make a world 90% of the time it uses the surface biome leading to blank caves

this is easier to show in a custom world with fewer biomes like two surface biomes or cave biomes I think it’s a bug 

I will upload a datapack I made that does this 3D biomes bleed 

It does it on the normal world that’s how I found it and started using datapack worlds to test 3D noise

got no picture yet

watch this YouTube vid it shows what I mean https://m.youtube.com/watch?v=Y35JVgDvLFQ 

when you add two or more biome layer cave biome also bleed to the surface it happens with just two biomes but its less noticeable 

i have added a datapack look for cave biomes and go up top and watch the vid for underground

my biomes are set up 3d so whats happing is not intended note with the pack biome are large so render my not show it on spawn

the desert is meant to be the only biome for the surface

found if i use -2 to 0 and then 0 to 2 for the two biomes it works as intended i think its for values in between the preset values