2 x 3 years would be 6 years. 1950 to 2022 are 72 years. So 6 years of 72 years would be 8,3 percent. YMMV if this can be considered rare
What if there was La Niña on 1952, 1953 and 1954? Your method does not account for that. Natural events and climate do not adhere to someone's made up "mod 3" date statistics.