Of course it has DisplayPort technology. You guys wanted what? The handheld to have an HDMI port to communicate with the dock? The dock would be unnecessary then.
The handheld uses this tech in order to pass power, image and sound through one single connector (USB-C), the dock then passes image and sound to TV through a standard HDMI.
I question that. I think the dock simply cradles the device to charge/pass video using a proprietary port which only requires the system to "rest" in the dock. If you watch the Jimmy Fallon footage, it did not look like there was anything inserted into the Switch from the dock when Reggie pulled it out of the dock.
It looked like it was simply sitting/resting in the dock and not "locked" into the dock. If it was using the USB-C port on the device when docked, Reggie would not have been able to so casually pull it out and it would have required some (minimal) force to remove it/unhook it from the dock.
I think it will sit in the Dock similar to how the Wii U Gamepad sits in the charging cradle.
See here at 7:42:
https://youtu.be/7TJ7IUNWGl4?t=7m42s
See? It doesn't look like anything was connected via USB-C. I think that will just be for portable charging and (maybe) sharing data.