Cos they are going too slow..?

I was doing anaerobic intervals today and passed a guy on a hybrid just as i was starting to ramp up, about 5 seconds into the interval (really strong headwinds too, so i was going fairly slowly). As I pass him, I heard him say "hi".

a) Under normal circumstances, I would not have heard someone behind me unless they yelled, and he would have likely thought me a dick
b) I gave him a raised hand acknowledgement, if for no other reason than to avoid the risk that he was a member here and would start another thread about arrogant roadies.