We ask the system about the installed profile for each display and try to use the profile correctly. So in our tests here, with a Thunderbolt display (standard gamut) and a Macbook (wide gamut) the two look identical, because we use different transforms for each display.
Is it possible that the external display is actually wide gamut, but macOS does not know about this? If this were true you may see other apps displaying colors that were extra saturated, and the fix would be to install a good ICC profile for the external display.