The question also seems whether there could be some confusing terminology with P3. My Samsung is advertised as having DCI-P3 coverage, but after reading up on wikipedia DCI-P3, my monitor much more resembles Display-P3, Apple’s adoption of DCI-P3 color space for computer monitors.
From the wikipedia article:
DCI-P3 specifications are designed for viewing in a fully darkened theater environment. The projection system uses a simple 2.6 gamma curve, the nominal white luminance is 48 cd/m2 with the white point defined as a correlated color temperature of ~6300 K.
Display P3 is a color space created by Apple Inc.[12][13] It uses the DCI-P3 primaries, but instead of the ~6300 K white point, Display P3 uses the CIE standard illuminant D65 as the white point, which is the most common standard for self-illuminated displays and devices (sRGB and Adobe RGB both use D65). Also, unlike the DCI-P3 projection gamma of 2.6, Display P3 uses the sRGB transfer curve, which is approximately equivalent to a display with a 2.2 gamma.
So DCI-P3 being the movie theater projection standard for a fully dark viewing environment it does explain the very high 2.6 gamma. It also uses the “odd” 6300k white point. Display-P3 on the other hand makes a lot more sense for watching content on computer monitors or TVs in dim lit (not fully dark!) rooms with its sRGB transfer function and D65 white point.
Out of the box my Samsung was set to its native SDR mode with wide color (P3) gamut, but with D65 white and a gamma curve that resembles something between an sRGB curve and a pure power gamma, averaging out between 2.3 and 2.4. Clearly closer to Display-P3 than DCI-P3, even though the marketing is saying DCI-P3.
It would not be surprising if most wide gamut monitors actually use Display-P3 spec and not DCI-P3 spec and there’s just a general misconcepted use of the terminology where everything P3 is just called “DCI-P3”?
Regardless, it could make sense to add Display-P3 to your shader instead of or as a complement to DCI-P3. The latter really only seems suited for use in a fully dark theater environment.