If that was the fundamental issue, ISPs would be talking about provider-agnostic throttling of usage to protect network stability and performance during periods

If that was the fundamental issue, ISPs would be talking about provider-agnostic throttling of usage to protect network stability and performance during periods of high utilization. Which is something they already do. What they're actually talking about, Re: Net Neutrality, is throttling a particular provider, regardless of the usage level of the network or the total traffic being streamed by that provider.