Well, interesting idea, but can you trust that it generates it properly? Because if it doesn't, then your understanding of the code will be incorrect, even worse than lack of knowledge; and if you do need to check all the things it has generated for you, as a description - doesn't it defeat the purpose of the tool?

Arguably, if you vibe code you don't really care about the code, thus even less about the diagram. So you'll vibe something, get a diagram of something to show your boss, and you can move on.