I expect we've all watched the HS cctv, aware of timings stated and seen/told the length of time this male was present, the same male we likely believe was driving a car that Libby got in. Personally, I feel there was time to "show" himself at the bench and there was time for thought. You could possibly say he was worried, but, didn't dare approach her initially incase he would be incriminated, it's possible. It's possible he just wished to know where she lived, so he could stand in the vicinity holding his penis in his right hand. However, in my opinion if you feel his intentions were to do more than "show" himself, how could he do this and be sure that it, whatever it was, remained a secret. That is relying upon a vulnerable young lady, presumably as a stranger, to either consent or not. Either way, is a risk to a married man with, it will seem, incriminating things to keep well hidden. Would a flash or a fumble be worth that risk, or was there more thought involved?