And since they eschew branches with names you get to memorize hash strings instead of branch names that describe the thing you were doing?

No trouble, you can still name branches if you want. And no, you don’t have to type the whole changeset hash, the first one to three letters are usually sufficient.

Also, branch names are not a permanent thing, they disappear after you merged them.

If you want, to can put an empty commit with the description of what you want to do at the top of your changes, and then use “jj split” to move changes to different commits before it. There are several common work flows which are explained in Klabnik’s blog post.