There must have been some sort of inconsistency in the reports for them to keep questions witnesses about his clothing, Or maybe they were just being thorough.
Since the residents really didn't know the actors well enough to identify them in the dark and at a distance, they were using clothing as the identifying feature. Also, the level of detail a witness can recall measures the amount of detail they actually witnessed and the accuracy of their recollections.
Two customers witness a C-store robbery. One claims the suspect was Caucasian one claims Latino. The
Caucasian witness also describes the suspect as wearing blue jeans, white running shoes and a black shirt with white stripes. The
Latino witness suggests the suspect "might have been wearing jeans - I'm not sure." Which probably either saw the suspect better or has a more accurate recollection?
You also want to get detailed descriptions to check against other witnesses. Let's say one of the cutomers in the parking lot never really saw the suspect or the robbery, but did notice a man with blue jeans and a black shirt getting into a certain car after the robbery.
It's just good police work.