I can't say I really get why he's an "NPC", other than the fact that the entire guardsmen group are pretty much useless besides the role of barking when stuff happens. They are all essentially kept as pets...
I think the guy would truly be an NPC, if he'd have absolutely nothing to reply in a conversation, other than the same one or two lines. Repeating the scenario in which he comes over and warns the girl about stuff, doesn't really cut it for me.