I'm not a Color expert, but setting my TV to BT2020 when playing a HDR movie, I can really see the difference. Any more technical details from your friend wesk05 ?
That's because skin tones are desaturated, when displaying a 2020 signal with 709 primaries, which is the default. If you manually set it to 2020 (technically DCI-P3), the colors are as intended. The box can output the 2020 color space, if you disable auto frequency switching or, more conveniently, set your GUI frequency to 23.976 Hz (or whatever frame rate your HDR content is in). This way there's no mode switch, when starting HDR playback and the TV will automatically go into 2020 mode. That bug was introduced after the nougat video code had been merged.