If you are required to provide anything, if you are required to stop and answer questions, if you are not free to say "piss off" and walk away, then you are being detained. Reasonable suspicion is the standard to detain somebody. I am not confusing it with probable cause.
Whether he's carrying ID or not, whether he's black or brown or red or white or green, is irrelevant. If the cop has reasonable suspicion that he is involved in a crime, then the cop can detain him.