Yes it is true.. Vincent from HDTV did a video about that topic too..
It also makes alot of sense from a "work flow" perspective. DCI-P3 is the color space used in cinemas.. So they work in movie or tv production with this color space.. scale it down to Rec 709 for SDR, and use DCI-P3 for UHD and cinema..
Also DCI-P3 has a wider color range by Rec 709, but not far away.. You could calibrate even old SDR TVs to that color space.
They should haven chosen DCI-P3 as the UHD color space..
2013 Panasonic TX-P42STW60 PDP
2013 Panasonic TX-P42X60E PDP
2019 Panasonic TX-40GXW804 LCD