They don't need to. The board explains it's there for them to post.
Since Admin have never raised an issue with the dodgy CH4 programme makers, I doubt they will with the BBC unless someone complains. They usually just ask for enough detail to be given so it understood what it's about but beyond that it's "buyer beware".
I agree though, they should be vetted but I don't know how they could do some of that given how some of these programme makers operate. For a start, there should be mandatory information like who these people even are, details we can check against, etc.