Player versus Environment or more commonly known as PvE.. The process of killing or participating events where the slaying of non player characters, or NPCs is the goal. Patrol is PvE. There is no denying that. While it's not the only way to interact with the game through PvE content, it's not a "part" of PvE. It's just one type of PvE event. A better way to explain it is it's a game type. Just like clash, skirmish or control are all PvP related game types, you have story, patrol, strike and raid. Different PvE game types.