This is immaterial to the case. An officer on duty is not prohibited from talking to someone he knows, even if that is not directly related to his duties. Even more so if it is in a public place.
Periodically, officers take breaks during the course of the day, for things like lunch, coffee, restroom, etc. But they are still on duty during those times, just excused from taking active calls, unless they are emergencies.
So using this lawyer’s logic if someone had walked into the White House while Bill Clinton was having one of his encounters with Monica and blew him away it would have not been a presidential assassination but just plain murder.