The author has a weird take on zero based budgeting [0]. To me it seems like a distinction without a difference. I never did try Firefly because at first it wasn't very mature and then later I found Actual Budget, which is (or at least was) perfect. (I haven't transitioned to the open source version yet, so I'm not sure if they broke it.)
[0] https://docs.firefly-iii.org/explanation/firefly-iii/backgro...