@lsitongia, as far as I understand, "Type C" only defines physical shape of a USB port. Inside it could be USB 2.0 or USB 3 or USB 3 + DisplayPort alt mode. Most mid-range phones only have plain USB 2.0/3.0 , and so video output is not supported.
Do you know, is that because it's the lower-cost version of the phone?
I think it definitely helps to reduce manufacturing costs. In case of Pixel devices the absence of physical video out ports also help advertising chromecast devices, I believe . Considering all the things I wouldn't count on support for video output over USB Type-C port on a phone by default, unless it is explicitly advertised in device specs.