As someone who kept track of this from the outside, my understanding is that Mononoke, which was that "Mercurial server written in Rust," eventually diverged from Mercurial proper, and is now a new SCM called "eden". It's also no longer a DVCS.
It is still an incremental/lazy DVCS, the first checkout does not download the whole repository, but for most users it looks like a DVCS.
Gotcha, I don't know about the details, I just know that their readme states very plainly that "Despite having originally evolved from Mercurial, EdenSCM is not a distributed source control system."