Everyone will work in the media they’re comfortable with. Traditional and digital media have some fundamental differences, but neither is inferior to the other. It’s kinda interesting how the scales in later years seem to be tipping towards favoring digital art to some degree - when I was a wee babby furry most people preferred traditional over digital art as it meant there was a physical original.
I’ve seen some really good traditional refs and some really bad digital ones. As digital art has become more prevalent it’s become more common for people to add RGB or hex color codes to traditional ref sheets, and many people I’ve seen that use common/large brand markers or colored pencils (Prismacolor, Copic, Tombow, etc.) will also note color names or numbers on traditional ref sheets.
I’ve seen more artists refuse to work with written descriptions than with traditional references, by far. I can’t honestly recall any that I’ve seen state they won’t work with traditional references - at most they might make caveats about color matching not being perfect (which can go either direction tbh - matching colors from a computer screen to physical media isn’t easy).
It might in some cases be less convenient to work from a traditional reference, sure. But the flip side is that people with traditional references are probably aware that they’re hard to color pick from and come in with expectations matching that fact.
