It doesn't matter whether you use BT.2020 or DCI-P3 primaries as long as you match the primaries in the Dolby block with the colour profile used by the display. Most LLDV displays use neither and the primaries are dictated by the display performance them matched with a colour profile the display uses in LLDV. The whole point of the LLDV hack is to use matching primaries in both the Dolby Block and the display and its just easier to use BT.2020 as that is generally used in the display's HDR10 mode which is easy to invoke. P3 works just fine as does pretty much any other sensible combination, although most displays are not agile enough to set primaries manually. There's really no reason to use anything other than BT.2020 since it's only a target (that's what HDR10 does). Claims that "the entire process ... Is incorrect ..." are entirely wrong and demonstrate a lack of understanding of how LLDV works.