You would need an agreement to meet the three-year minimum for the very small number of individuals who perhaps reached 65 years of age with only one or two years of residence, but otherwise the agreements would not affect the payment of old age security benefits in Canada.
However, I should add that it would affect the payment of old age security benefits outside of Canada, because we still have a 20-year requirement for the payment of the benefit abroad. A person who lives in Canada for 15 years could export that pension under an agreement through the totalizing provisions.