The technology they are using basically is similar to the technologies other wireless providers have used for throttling which they sometimes call "video optimization", the word optimize here is from the perspective of the carrier meaning "use less bandwidth on our network. It works by re-sampling and reducing the video quality in terms of resolution (pixels) and also color fidelity (e.g. octree). The thinking is that people watching video content on their phones will not notice the difference because the screen is so much smaller. The reason a lot of carriers ran afoul of NetNeut is that they were applying it without the consent of the subscriber (for example some would apply it only when their network or a cell site was nearing capacity or for users who were "abusing" unlimited plans (abusing meaning actually using a lot). I am not sure if the user elects to use a service with reduced quality at a reduced cost is really a violation of Net-Neut or not, the cable companies offer regular definition and high definition TV at tiered pricing for example. All the wireless carriers are trying to get into the content business in various ways as the growth of the traditional business levels off.

One add on to my own comment is that I forgot is that there is an allegation that Tmo is applying "video optimization" to content other than bingeon, which if true is a clear violation. It also is possible they are just incompetent too because that type of system they are using has to be programmed based on the 5-tuple source or destinations (and some other parameters) which it would not surprise me if they screwed that up).