I guess this isn't a critical issue since you can always not use hasher but at the very least, it may be worth noting this in the docs since people may get worried about this
EDIT/UPDATE: I was thinking about it and other things leak names too like the vfs-cache so it is important to know that. Except if I am mounting something, I can nuke the cache when I am done. If I nuke the hasher kv store, it doesn't do me any good. I guess I could encrypt that too but it is a bit ridiculous)
The name leaks should only ever be local, as in the VFS cache.
It will kill off the record of the local names, if that is what you mean?
You could always try putting the hasher after the crypt instead of before, so it keeps track of the encrypted hashes. Maybe not very useful, but it will mean it doesn't get access to any of the real names of the files!
I think there is a lot of things in rclone that leak file names to the local computer. Cache backend, VFS caching, logs, kv store, stuff in /tmp and more that I can't think of right now.
I'm not sure adding encryption to the kv store will be enough to plug all the leaks.