Arrieta's ERA in August was 0.43. See how dumb your argument is getting? This is circular and you are reaching.
This is overall stats + more recent stats being weighted more than stats in April. But they ALL count.
Arrieta is the best pitcher in baseball in 2015. And he's not getting this artificially low ERA by pitching in Dodger Stadium. Jake got a start in Dodger Stadium very recently. Remember it? LOL. I'm sure he'd love to pitch there all season.