I strongly suspect that here we have a perfect example of how this could be cleared up with some simple communication on this board from Steinberg people.
This is speculation but here is what I think is going on:
Steinberg in the development of the new video engine is testing out each on every video resolution and color space that is being sent to external video. They are making the assumption (a good one, if this is true) that YUV 8-bit video is the most common spec that is going to be used when sending a video clip from one post house to the next. Outputting to RGB video is highly unlikely and sending 4K comping videos to sound people is VERY unlikely and easily prevented by the sound house sending a SPEC SHEET to the supplier. So in order to get the new video engine out the door decisions were made to reduce the time required so they punted unlikely video resolutions/color spaces. The truncated list shown is exactly what is the most common of formats: it’s in YUV color space and 8-bit encoding, so the files are not silly huge when sending to various suppliers in the post-chain. If it were VFX houses, it would be different.
Again all speculation but I could see this being an entirely rational management decision from Steinberg but why do they not communicate with us except for the odd but helpful individual that surfaces from time to time?
If people here are having problems, with the video clips, you should reconform your videos to YUV 8-bit HighDef files and it ought to work.
Looking forward to the 8.1 update that appears to be around the corner. Thank you Steinberg Devs for all your efforts.