This message was posted on behalf of Intel Corporation
In regard to your concern, I did a research and these are the details that I get for you:
Intel resolved early display quality issues encountered on early hardware through a firmware update in 2011. The interface employs two data channels, each capable of pushing 10 Gb/s in each direction. The solution used one channel for the I/O device and the other for display signaling. Even still, we cite 10 Gb/s as Thunderbolt's official spec, since performance is not additive.
You can see a clear reference in the image attached as; thunderboltcable_bandwidth_600px.
Also, you can find more details of Thunderbolt Technology at the following link: