When are emails not relevant.

I was told by David Bell, lawyer for the Vancouver Health Authority, that emails and other notes were not relevant. This was against my understanding of what discovery of documents meant in a litigation proceeding. Each party has to disclose everything even the kitchen sink. If the documents were not relevant who decides what is relevant. It seems that David Bell decides what is relevant or is not relevant. Does that mean David Bell will only produce documents that are good for his client and other documents that could provide evidence to the detriment of Bell's client do not have to be disclosed. This is bizarre. In the Dominion v. Fox case, Tucker Carlson produced all his emails i.e. the kitchen sink. I would assume that it would have been up to Dominion to decide if documents are relevant or not. Maybe in the US document discovery is different than in Canada. I am very confused.