I had a big feature I was working on. jj made it easy to split it into 21 small commits so I could give reviewers smaller things to review while I continued to work. It wasn't perfect and maybe git can do it all by itself but it's not my experience.
In other words, I effectively was working on one thing, but at a quicker easier pace.
I've been doing this in git for years. Interactive rebasing isn't that scary. At work we have a very big stacked PR culture on github using native git