Well they can see everything but cannot necessarily distinguish everything. Our approach is guided roughly by this image's intent (not this image specifically, just for illustration):
View attachment 47359
Duet/Prot have similar perceptions - in that regardless of how and what color we see, they
can see varying shades of browns, blues, and yellows. Tritanopia folks
can see pinks, reds, and turquoise-like blues. So rather than rely purely on contrast, we pick the color palettes directly from the colors that are visible to people with various colorblindness types. That at least has been our approach so far.
Normal OK buttons (for features that succeed) are green. For colorblind palettes, no one can see green effectively - but all can see blue - so they are various shades of blue.
Question - you say "virtually no difference between the 3 on the right" - It is true that Deut and Prot are nearly identical - you can see from the color palette above their perceptions are also nearly identical. However there is a massive difference when using Tritanopia. So I'm wondering if you've actually tried them out, or are basing that assertion purely on the little icons above the color palette names.