Why is T-Mobile 5G more like 3G?

Are you watching Netflix on your phone using the mobile Netflix app?  Obviously, congestion will impact data speeds along with the bands deployed where you are and are using the device.  I have never experienced throttling though as a T-Mobile customer and I travel through some of the largest cities in the country each year, including up to Canada.  If you are tethering, T-Mobile will throttle certain types of non-mobile traffic and traffic routed through a VPN.  On 5G, It's incredibly rare to see download speeds below 150Mbps and 200Mbps is usually the minimum I see when streaming content.