There exists multiple implementations of the mercurial loader.
Only one is now the official swh.loader.mercurial.from_disk.HgLoaderFromDisk.
The other implementations helped for backward compat when crafting the new one.
Now that's it's landed and used, those should be cleaned up to avoid a high burden maintenance.
The official one should be renamed to swh.loader.mercurial.loader.HgLoader.
That might be a blocking point for  so that may have to come before it.