I don’t get what your point is. Is there a requirement that one must be a dual citizen to renounce their citizenship?
No, Section 17 only deals with natural-born Canadian citizens who at their birth became by the laws of another country a citizen of that other country. Section 16 deals with Canadian citizens who naturalize in another country, Section 18 deals with the case of a minor child whose parent gives up the parent’s Canadian citizenship and so on.
A child who meets Section 17 requirements at least until the age of 21 years is a dual citizen.