Photoshop is removing something that GIMP doesn't even have - PANTONE colors.

We added import support for most Photoshop palette formats (ACB, ACO, ASE), so you can use them in GIMP. I don't think we can directly include Pantone palettes in the install because of copyright issues, but if you already have them, they should work fine in GIMP (and if not, let us know so we can fix it!)

Not adding format features that you are not willing/able to maintain in perpetuity is a positive, yes.