I'm not sure we 'know' that they clipped right wings, that bit seems to be in the paper but not the NTSB report. And I guess they may have been in the location of the downwind leg but not actually both flying downwind - or as you say, not to the same runway. Eyewitnesses are notoriously unreliable too - 'opposite directions' could also be converging headings but seen from behind.
The phenomenon of aircraft on a collision course not appearing to move in the windscreen is (should be) well known. These tracks, flying at different speeds, collide at 90 degrees and have the same relative bearing to each other. Unfortunately, by the time one aircraft 'blooms' there is often very little time to react.