Yaz had an interview earlier where he said he had never heard of BlazBlu, and Kat happened to choose a character that he didn't know how to deal with. The guy didn't even know how to hold a stick, fighting games are one of his worst genres.
And apparently the time they were home was only like a couple days, even though it seemed longer. Yaz said he was playing the games all day every day, and only got about 8 hours with each.
As for Halo: Reach, apparently Kat was already a champion halo player, and Yaz doesn't really play console games. He obviously was trying to play like it was a war shooter, using cover and aiming carefully, but you don't need that in a game with aim assist. So kat just flew all over the place and headshotted him.
Then again, the youtube videos of yaz playing CSS are pretty ridiculous, so who knows?