The notebooks aren't evaluated in reverse, but rather in the order they need to be to get the final results. Observable builds a DAG, similar to Marimo. You can put cells in any order you'd like.
I think that in all the notebook solutions I've seen that allow this, a culture emerges where the "final result" is put at the top so that you can find it easily and interact with it as a user. The actual development process involves writing stuff top down and then re-ordering it for use.