This draft spec was eventually published as RFC 9562. Compared to the previous spec it adds versions 6, 7, and 8, plus best practices guidance.
Basically, there are a bunch of UUID alternatives that arose to fix the problem that UUIDs are bad for use as database keys in large tables (here’s the perspective of MySQL experts Percona). A bunch of these alternatives are actually linked from the RFC, which I haven’t seen done before. Version 7, in particular, is meant to address this use case.