It's not about seeing different colours, it's about seeing details from the brighter highlights.
Colour blindness isn't just about seeing different colours, I mistake different hues of colours, HDR is a wider colour range (Due to more brightness and deeper blacks) so more hues.
The issue is in certain colour spaces I see just one colour whereas you would a full range of the spectrum. For example pale pinks like Will just look grey to me, A whole range of Pale reds and Pale orange will just look Brown to me.
The detail of colour is the range of hues in the spectrum, and that is exactly what I mistake for certain other colours or just don't see at all.
As a Deuteranope I confuse very commonly
1. Mid-reds with mid-greens
2. Blue-greens with grey and mid-pinks
3. Bright greens with yellows
4. Pale pinks with light grey
5. Mid-reds with mid-brown
6. Light blues with lilac
Believe me I've looked at HDR content on HDR vs SDR and the difference to me is extremely minimal, I can tell it's different but it's not that mindblowing at all where as people looking at the same can tell a very big difference.