I was trying to login into my adwords account and by mistake I entered adsense login info, what I get is following. Read the below (in blue), is google saying that you buy traffic with adwords and earn more with adsense??
I don't think that they are specifically promoting arbitrage. I'm guessing that that part is actually meant for people who have their own sites, advertise in Adwords and who are then looking for extra revenue. The main goals of those sites is not to have people click on their Adsense ads, but rather to buy a product/sign up for a service etc. The Adsense is just a nice way to generate more revenue. At least that's my understanding.