As a source control expert and jj's number one fan [1], I would count being able to defer merge conflict resolution as a new capability, FWIW. In general I think jj's greater than the sum of its (very good) parts because of how its features work together to create a coherent and pleasant user experience.
[1] the top testimonial on https://jj-vcs.github.io/jj/latest/testimonials/ is mine