This is just me speculation, it might be nothing.
So I have a couple of onslaught game where my team did very well, no one feed, we kill enemies, both team kill command ship at the same time. And then we lose, by a big margin (not the above, but there are games we lost for more than 1k3 points), and not even by the last command ship race.
I just took an example in the picture, you can see my team have much greater scores than opponent's, but we lost.
Is there any explanation for that?