No, you've misinterpreted the rules. The war was a 20vs20 - you don't receive points for bringing stragglers. The rule you quoted above is in place for a war such as a +/-5, where the number of opts is still undecided; or a matched war (20vs20), where one side only pulls 17 and their opponent agree to drop three, even if the rules say they don't need to. In this war, the decision was already taken that it was a 20vs20.