It is a rule that you get the deduction for the knockdown, but I'm pretty sure (not 100% tbh) it is also a rule that you have to score somebody a 10 I believe.
ex) say each player scores a knockdown on the other, but one clearly dominated the fight. That score would be 10-9 I'm pretty sure. Because Technically both lose 1 point for getting knocked down, so that would be 9-9, then the person who clearly lost the round gets another point deducted so it would be 9-8. But you can't score it 9-8 on the card because someone needs 10. So what you do is raise both scores equally until you have a 10. So it would be 10-9, even though both got a knock down... Basically the knock downs cancelled eachother out in that scenario.
So with Garcia and Tank, if the judge thinks Garcia loses a point for the knockdown, but otherwise won the round (and it helps it looks like he wasn't really fazed by the knockdown), it's not crazy imo to have that 9-9, which then you need to raise it so someone has 10, so it's 10-10. What most people do is see a guy got knocked down, and unless he unquestionably won the round, you score the round in favor of the boxer who scored the kd.. so it'd be 10-8. And IF that boxer that suffered the kd unquestionably won the round, usually they still only score it 10-9 which is more like saying the round was a tie, and the guy lost a point for the kd. So in a way that scoring isn't actually reflective of how the round played out - 10-10 would be... But Idk I'm not an expert on boxing scoring lol...