> They don't need to write any rationale on why they made it
Just next tho the "experimental" moniker, and within an actual section about Rubocop, they in fact did provide a simple rationale anyway.
Checks out for me (even if they didn't have to provide any).
(emphasis mine)
> Why Not RuboCop?
> In most cases you likely want to use RuboCop as it has more robust support and testing. This gem is currently more experimental and focused exclusively on refactoring and AST manipulations in a more minimal sense.