That's right, except that a boat who sails in a class of only 2 boats will have a lower maximum score when calculating BotY, giving her an advantage over boats who have to compete against a larger class for any given regatta or series.
That's why I said the bigger mistake would be to let the ratings stay as is for the current series. Girl and Evil Intentions will have an advantage over Zephyr and Arethusa, for example.