The term vibe coding actually originated from a tweet from Andrej Karpathy and so there is actually a sort of definition of the term. He said vibe coding is where you "forget the code exists":

https://x.com/karpathy/status/1886192184808149383?lang=en

So if you "read the diff" it isn't vibe coding, at least not by Karpathy's definition.

Obviously it's not a "rule" and you can still call it vibe coding if you want to. Maybe the meaning of the term has evolved since his tweet anyway.

Well, that's literally what "vibe coding means", no?