No it’s not a hybrid effort (except insomuch as LLMs are reliant on human generated data for training). They’re simply saying that the code created by the LLM can be examined and potentially understood by humans.
It can work by itself too but it is unclear at a glance how well since the main focus of the paper is the new mathematical benchmarks they achieved, i.e. their best results. Will have to read the paper more closely to say anything with high confidence, but based on their summary I'd guess the human in the loop part was pretty important here.