And with 2.3M customers, that's an average 1.7 Mbit/s per customer, or 550 GB per customer per month, which is kinda high. The average American internet user probably consumes less than 100 GB/month. (HN readers are probably outliers; I consume about 1 TB/month).
But that’s me.
I don't think that breaks net neutrality either, which the FCC seems to be reimplementing
Edit: see https://openconnect.netflix.com/en/
T-Mobile absolutely counts all data used over the network, my voice lines go QCI 9 (they are normally QCI 6) when over 50GB of any kind of data usage each month, the home internet lines are always QCI 9. I don't have congestion in my area so it does not affect my speeds. This is QoS prioritization that happens at physical sector level on the tower(s).