IMO, the main use case for LLMs in unit tests is through a code completion model like Copilot where you use it to save on some typing.
Of course, there are overzealous managers and their brown-nosing underlings who will say that the LLM can do everything from writing the code itself and the unit tests, end-to-end, but that is usually because they see more value in toeing the line and follow the narratives being pushed from the C-level.
