Sometimes it does need to be specified as a group dynamic - if a group is racially uniform (say, it’s a historical novel set in Viking-era Iceland, obviously everyone is going to be white. But fast-forward a few years to the Viking incursion of Vinland, and you have both Vikings and First Nation people mixing, and at certain points, intermarrying). You may need to specify for reasons of the story that the group is racially uniform or diverse. It’s a bigger problem in science fiction and fantasy, since PoC’s are not widely represented in the field. Writers who want to make sure that their characters come across as not being white have to make it explicit that their character is not white, usually with physical descriptors. I write science fiction, and the one I’m working one has only a few white humans, while the rest are various other shades. But since white people tend to be the largest consumers of science fiction at this point in time, if you don’t specify “Yeah, this person is black, this one is Southeast Asian, this one is Hispanic”, readers tend to picture them as white. Which is probably how Johnny Rico, described multiple times as a Spanish-descended Filipino is played by a Dutchman.