I don't think that's a fair characterization.

It's more that there isn't really a big difference between the workflow of

    # you're on
      staging area
    @ commit A
    # make some untracked changes and console logs you don't wanna commit
    git add -p && git commit # select only what you want

vs

    # you're on
    @ empty commit 
    | commit A
    # make some local changes (which are tracked in @)
    jj commit -i # select only what you want

You're still "in charge what gets tracked" if you treat the last @ commit as your local playground, exactly the same as the staging area. The only difference is that you can use exactly the same tools to manipulate your "staging area" as other commits. The only difference being that you can manipulate your staging area with the same tools as any other commit.