Unrelated but I'm curious about their choice of programming language. It doesn't look like they're writing their own Lua interpreter anyway, so it feels like they could have selected a different language.
Author here, what question do you have? I'll eventually be writing my own Lua interpreter but the whole stack is designed to (and currently does) bootstrap from standard Lua 5.4 (or 5.5)
One thing that could be different between a programming language and everything else is that by writing in Lua, you're committing to the whole language surface. Whereas I imagine with other things you have the option to make your own design choices?
Lua is a very small language though and sandboxing it to specific global functions is trivial