/wb fill does not genererate caves from y=-64 to y-0

[Tsoccerguy3]

On maps created on Minecraft Pre 1.19.x that are now running on 1.19.x . A Serious error , /fill does not fill in any chunks with cave from y=-64 to y=0 unless players have visited the chunks

Here is the render of layer y=-64 ( courtesy of MCAselector ) , after a /wb fill is run on a map in Paper 1.19.4 . The Slate is viable on any chunk that has been visited in 1.19.4 . All areas that are black , the fill command has ignored the chunk FLAG to generate caves.

[Tsoccerguy3]

This is a big flaw in worldborder, so we switched to Chunky and Chunky Border . I will leave this here for people that have same problem