Well, IMHO, nowadays this classifies as bad design. It may have been the better design, but currently git's nomenclature is the standard and not complying to it will only hurt mercurial.
Mercurial and git were initially released within a couple of weeks of each other. To change terminology now would break ten years of backward compatibility.
I used bookmarks back when I used Hg, which is a couple of years ago, but I had some problems with them. From time to time bookmarks wouldn't update remotely. This made me always push twice, to make sure the bookmark was updated. They've hopefully fixed that now, but it was one of my main gripes with Hg. That, and that the Jira version we switched to didn't support bookmarks.
If your workflow fits better with git-style branches, you should use Mercurial bookmarks, not Mercurial named branches.
Mercurial even tells you:
every time you create a named branch.