I thought it was a little bit later in the book, but yeah. The point may have been to point out to the reader that the character’s race was really irrelevant. There’s also a scene earlier where we find that Rico’s parents were in Buenos Aires, so some readers might jump to the conclusion that Rico was Argentinian or at least a Latin American. Heinlein, of course, tells you that such a conclusion would not be valid.
Another SF example is Neal Stephenson’s Snow Crash. In the first chapter (ish), it is briefly mentioned that the main character is black. The topic is immediately dropped and I believe never returned to again. The point being that he’s black, so what?
I write for children and unless some physical characteristic is absolutely necessary to the plot, I don’t describe my characters at all. Let the illustrators use their imagination.
Ever read the Solar Pons stories by August Derleth? Actually quite good, but Pons’ landlady, at 7B Praed Street, Mrs. Johnson, is almost always described as “Well-scrubbed.”