minecraft end biomes being generated wrongly

this occured on a minecraft server that was upgraded from 1.17 to 1.18 hosted by hypixel smp 
https://www.youtube.com/watch?v=z_IsAgc-KWU&ab_channel=Spyder981

no plugins, no worldedit, only the default vanilla one 

The biome in the end changed to planes in newly generated end-chunks

Mobs as well as bats are able to spawn there (look at the video).