I think it's a case where Verizon is dropping the ball with their connections at the peering points. I've noticed a big difference in the quality of streaming from Apple TV and everything else on FiOS... Netflix via Apple TV is routed a different way and that seems to be pretty reliable whereas on Xbox One, Roku, PC etc... is embarassingly bad.
However if access Netflix via a tethered AT&T 4G phone in my house the streaming is fantastic. I know it's far from scientific but it does seem most likely to me that it's a problem at the point where the traffic enters the Verizon network as the traceroutes on ATT seems to show the content is being served up from the same location. Makes me suspect that Verizon is dropping the ball without enough capacity for the traffic at the handoff point leading to poor performance.
Verizon does a good job selling users on "the power of fiber optics" but that all seems meaningless if that only translates to decent speeds as long as you don't need to decent bandwidth to services outside of the Verizon network.