MP4 with Dolby Vision to MKV

[ChocOrange]

It can play it, sure.  But is it transcoding?  Is it actually HDR?  THe DV spec for profile 5 requires MP4.  If something can handle it in MKV that is out of spec.

It is most definitely Dolby Vision as my Lg TV pops up with a playing Dolby Vision message, not HDR and not transcoding at all.

I think you are confusing mp4 video with the mp4 container format. Both are named the same but are very different. One is a file format and the container is more like a zip file.
Dolby vision mp4 video format can be added to the mkv container format and played with compatible hardware.
Let's not forget the Nvidia Shield is fully certified for Dolby Vision so it won't play 'out of spec' files. Their license would be invalid.

Care to share your link for the DV spec requiring mp4 for profile 5?