Fair that I don't intend my question there as a full rebuttal. I do question if functional semantics are fully needed any more so than other tools. In particular, I recall formal methods was more about prepositional logic than it was functional semantics.

And yes, you have to add and remove things to any model to really be able to reason about it. Is why engineering dynamics is harder than engineering statics. Things that change are hard. Reducing this to state being the enemy, though, I think is wrong in a lot of functional advocacy. State can be reasoned about without having to boil the ocean, as it were.