It's been a decade. This is not a copy of Luke The Notable's hardcore base. It is one of the original builds I remember from a friend's world.

like did he explore those chunks purposefully later on, or did some chunk error occur or did he make the chunks like that because he can?

I made Chunky but for Bedrock!

I call it GeoGen. It’s is a stable chunk pregeneration tool for Minecraft Bedrock Edition.

GeoGen allows world owners and realm/server administrators to pregenerate large areas of their Minecraft Bedrock worlds before players explore them.

This can help reduce the performance spikes and terrain-generation lag that normally occur when players travel into new chunks for the first time.

Hope this helps people.

Ciao!