It's not just Netflix - the entire Internet works this way. End-users send a request, and servers send a response. There are very few cases in which the response is not larger than the request. It doesn't matter what content you're serving - the raw traffic delivered to consumers is going to be greater than the raw traffic from them[0].

Saying that they didn't know that the traffic would be shaped this way is saying that Level 3 doesn't understand the way the Internet functions on a technical level, which I would say is impossible.

[0] This is (sort of) why residential Internet speeds are usually quoted asymmetrically (e.g. 20 down/5 up). Consumers - well - consume more traffic than they produce, so networks are already optimized for delivering more traffic to consumers than they themselves generate. That said, all of the traffic is initiated by consumers; the traffic Netflix sense is only in response to the explicit request by a paying Verizon customer.

You'd actually bet money, on the idea that Level 3—a major internet company—didn't understand a fact about internet traffic that's blatantly obvious to everybody? What?