For those that don't care to watch the video, http://fast.com is a speed test hosted on the Netflix servers, so cellular data treats it the same way they would treat streaming netflix. It ranks consistently slower than Google's speed test, or speedtest.net unless you access it through a vpn. If you access it through a VPN to trick the carrier into thinking it's a different host, you'll get the same speed across the board.
For reference, ATT gives me 4.1Mb/s on fast.com, and 19Mb/s through speedtest.net.