I don't have any special knowledge of this, but it's possible at large companies for both to be going on. The people who don't like the tool move away, and the people who like it try to address some of the complaints to try to dissuade other people from jumping ship, and if they're very good at it, possibly convince others to come back.
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."