I am only have a passing acquaintance with them I'm afraid, though I have been meaning to get my head around it and write a few hashlangs.
https://docs.racket-lang.org/guide/pattern-macros.html#(part...
I like the explanation there, and I think it gets me closer to my objection. I'm quite happy with the Kleene Star as a concept, but I don't think it corresponds to any usual use of ellipsis, nor is it really a list element on equal footing with the others.
It's trying to unify how macros produce syntax objects via `syntax-rules`-style pattern matching and ellipses with how regular pattern matching on values works, so there aren't two separate pattern languages (one for macros and one for everything else).