I took the time to do some testing.
I downloaded the original versions of the LG Chess Demo and Samung's Quantum Dot Demo and saved them to a USB stick to use the TV's internal media player to render them in HDR.
I then played the Chess video in the following ways.
1. In HDR on the display's internal media player.
2. The Youtube version you linked via my HTPC to the Hisense in SDR.
3. The original video file via my HTPC using madVR's HDR handling to convert the video to SDR on the fly.
4. The original video file via my HTPC turning off madVR's HDR handling to intentionally send the video with incorrect colors/contrast.
5. The HDR->SDR converted clip on Youtube I linked to earlier.
What I found was that, despite the disclaimer on the HDR Youtube video, playing this back in SDR appears to not be sending HDR as SDR to the TV. When I compared it what it looked like when I intentionally sent HDR as SDR on my PC, the intentionally incorrect version was noticeably drained of color and contrast. The Youtube HDR video just looked muted. It actually looked similar to the PC image when madVR's HDR handling was on. This didn't come through in the picture you posted.
The tone-mapped Youtube video *does* look like it has oversaturated colors as you said, though the contrast looks about right.
HDR via the internal player does fall down on some of the scenes, but also looks noticeably better than the SDR versions in others to my eyes. This is consistent with a video intended to give LCD's trouble, though. Again, this video was created as a marketing tool to show why you should spend more for an OLED. I wouldn't call it representative.
I recommend giving this one a try. This one is intended to look good on an LCD.