A couple things to take into account.
1. Your time,server time and your opponents time are going to vary significantly. So what might look like walling on the replay is just the opposite. I have shot numerous rounds into someone only to see on the replay I never shot a single time.
2. Technology has come a long way and the advancements in sound make a world of difference in gaming. I received the comment just last night that I must have amazing hearing. When in fact I have $150 headphones that process the sound from either the left or the right side that my opponent is coming from. Could that be seen as walling? Probably....I wouldn't doubt it, but in the end it is not.
Does that mean use silent steps when prancing around my shotgun? I would if I were you, but in the end I am not