I think if your opponent forgets to do something, it's on you to remind him. Generally, people play within the rules, but if you let them do something they shouldn't be doing, that's on you. When the game ends, it should end, no matter how it played out. If your opponent had 102 points, you should have checked before it started. If he broke a rule during play, shame on you for not knowing the rules during the game. If you allow vacating a win based on a squad point total error, it just allows people to try to win, and then if they don't call out the rule violation for a free win. Bad policy.
I do think this Swarm Tactic outcome should be FAQ'd somewhere though. It's not an expected result of the card's text to most people. I can see in some tournament somewhere a big argument happening because someone doesn't want to swarm in a detrimental way. If there was a FAQ, it would end the argument quickly.
Every card doesn't need a freaking FAQ because people want to interpret the card in a certain way.
Step 1:
Read the card
Step 2:
Apply the card as it's written
Step 3:
Don't try to make something up just because you think it should be there
Just like Enhanced Scope from above, you can't choose when you want or do not want to use the card ability. You must follow the card as it's written. Don't over think it.