I think it is mostly about being able to declare the config schema in the same language. You can declare a base config file with types instead of values that has to be extended. The parser will validate the types and insert defaults when it is merging the configs. It also has some nice features to avoid duplication and boilerplate.

References: https://github.com/cuelang/cue/blob/master/doc/tutorial/basi...

Disjunctions: https://github.com/cuelang/cue/blob/master/doc/tutorial/basi...

Templates: https://github.com/cuelang/cue/blob/master/doc/tutorial/basi...

I also flicked through to find a little example use case and solution, but was disappointed.