For a small ISP there might be a much higher quality backbone link to one video provider than to another. This is probably a coincidence.
Also, popular services such as Netflix result in the build out of more dedicated bandwidth that is shaped to match peak demand.
Broadly, traffic shaping happens from QoS rules, ISP upstream provider choices, backbone infrastructure build-outs, etc. It's not a static system.
I guess my point is that this is too complex a thing for regulators to understand or to regulate in a sensible way. I prefer simple antitrust enforcement of last mile providers, even if it entails the government "confiscating" the transmission lines installed by ISPs and any of several ISPs to use them to serve a customer based on the customer's chosen ISP.
And the specific regulation of "Do not throttle or shape legal traffic based on origin or contents" doesn't require large complicated regulatory intervention. A simple complaint system "we observe that traffic to origin X exhibits dramatically different performance than traffic to origin Y" and response would work basically fine. Of course it would be better if ISPs would behave reasonably without regulation, but we can see clearly that it's not the case.
And we're not seeing network capacity greatly increased through sensible traffic shaping - that's an assertion made without evidence. If that were the case, we'd expect different video providers to be shaped the same way, and we'd expect the throttling to change based on time of day and peak traffic, which the researchers did not observe.