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.
But in general you are one of the few that does. Many devs do find git rebases scary. Having done it in both I can say with JJ it is much much simpler (especially with jjui).
In other words, I effectively was working on one thing, but at a quicker easier pace.