Good morning, Lars, I may still be asleep, but my sense of (IDs = IETF-IDs + Other-IDs) is that you're saying in the current text that the Internet-Draft repository contains all IDs, but it really contains IETF-IDs, right? If so, I'd suggest s/The Internet-Draft repository/The IETF Internet-Draft repository/.
<sigh>No, _the_ Internet-Drafts repository contains _all_ I-D's. Anyone can submit an I-D to the repository. Not all I-D's are working drafts of the IETF; some may be working documents of other groups. Hence the original language, which said, "other groups may also distribute working documents as Internet-Drafts".
It doesn't say "other groups may mirror the I-D repository", though that is certainly true.
It doesn't say "other groups may call their working documents 'Internet-Drafts'", though I don't think we have any means to prevent that if someone wanted to do it.
What it does say is "other groups may distribute working documents _as_ Internet-Drafts" (emphasis mine); that is, via the same mechanisms used by people preparing working documents of the IETF.
I vote for leaving the language as it currently is, instead of trying to rewrite it to say something else.
-- Jeff