Yep, exactly. To put it in layman's terms.... Level3 doesn't run the trucks on the roads, Level3 manages the roads themselves. Your ISPs are just sending traffic over those roads.... trucks don't do well on roads that are bad.
To get a better idea of the network, page 2 of this really makes it clear: http://www.level3.com/~/media/files/...twork-map.ashx