Rhino 8 GH1 Grids, Baking & some Concerns discussion continued

I might find the answer to this question by experiment or in documentation somewhere, but can you please elaborate on the Update mode of Bake? Suppose I change a curve, for example, in some way (extend or move control points) and bake it in update mode? How does it decide whether or not to delete the previously baked geometry?

P.S. In my own rudimentary effort at bake to layer 3.5 years ago, I handled this with a DelAll (Delete All by layer) component, using the same list of layer names used by the Bake components (plural, one per layer in that case).

Does this R8 Update mode of Bake do the same thing? Assume that all geometry on a layer gets replaced by the bake? Otherwise, how does it know if geometry has significantly changed? (a box becomes a sphere, for example)