what is the point of SDR ITU-R Recommendation BT.2020
I think this would be the most appropriate place to ask since you need a video processor of some sort to do this but...
On UHD-dics, to my knowledge, HDR and BT.2020 are a package deal. There are no SDR BT.2020 sources. So if you can't do HDR on your equipment what is the point of tone mapping HDR to SDR while retaining the BT.2020 color space?
You probably have a 1080p set (that is incapable of representing WCG accurately) and in such case and I would assume that one would want to tone map BT.2020 to BT.709 and HDR to SDR as that would be in line with the displays' capabilities.
Yes I did use the search but came up with no reasoning for it.
My gear: Panasonic TH-42PF11EK pro plasma display + TX-P55VT60E -- Iscan Duo video processor -- i1 display 3 colorimeter -- i1 pro 2 spectrometer -- Apple TV 4K -- WD LIVE TV gen 3.