That's not true in BC (well it is true Crown does charge approval) - often defence counsel and the accused present a statement to the Crown before Crown decides whether to approve charges. This is true in simple assault cases as well when it's looking like a he-said-she-said thing. The accused will simply write out a statement - their side of the story - and Crown will get a sort of preliminary idea where the testimony of each side is going to go. Defence lawyers assist in making sure this statement isn't inculpatory. 

Defence also can speak with the Crown directly before charge approval. Further, if charges have been approved, Defence can still push for a stay of proceedings in the same general manner as above.

It's a strategic decision. Sex assault and simple assault he-said-she-said cases are sort of an exception where getting the client to talk, and tell their side, is often good for the defence as it may deter the Crown altogether. Most other offences - a quiet client is best!