That assumes that before you have a thing in your hand (a working program with expected input, and output), you can exactly describe how that thing should act, what it should look like, what the input and output should be (and not be) and have that be successful - and structured correctly internally the first time.
In my 25ish years of experience writing code? That has happened for a non trivial task exactly zero times.
If the idea is you could refactor the UML (and hence generated code) to adjust, since none of the tools are able to generate functional code (stubs and simple templates yes, but not much more than that), that means it would need to refactor a bunch of human manipulated and generated code without breaking it. Which I think is well beyond even our current capabilities.
In my 25ish years of experience writing code? That has happened for a non trivial task exactly zero times.
If the idea is you could refactor the UML (and hence generated code) to adjust, since none of the tools are able to generate functional code (stubs and simple templates yes, but not much more than that), that means it would need to refactor a bunch of human manipulated and generated code without breaking it. Which I think is well beyond even our current capabilities.