> generated code can be verified by compiling and running it

I think this gets to the crux of the issue with LLMs for coding (and indeed 'test orientated development'). For anything beyond a most basic level of complexity (i.e. anything actually useful), code cannot be verified by compiling and running it. It can only be verified - to a point - by skilled human inspection/comprehension. That is the essence of code really, a definition of action, given by humans, to a machine for running with /a prior/ unenumerated inputs. Otherwise it is just a fancy lookup table. By definition then not all inputs and expected outputs can be tabulated, tested for, or rewarded for.

I was talking about the RL training process for giving these models coding ability in the first place.

As far as using the trained model to generate code, then of course it's up to the developer to do code reviews, testing, etc as normal, although of course an LLM can be used to assist writing test cases etc as well.