This sounds really good, and I would do it, but I am trying to disable monsters without disabling all mobs. If I wanted to disable mobs I would just use /gamerule DoMobSpawning false
Edit: Well, I watched through the video and near the end, the guy was flying around the world, and there were still some packs of animal mobs wandering the world. I don’t know if they spawned after he activated the mob switch or if they were already spawned prior or what. But if animals still stick around, then he’s just being confusing; because through the entire video he keeps saying that the contraption turns of “Mob” spawning, not “Monster” spawning. Animals are classified as mobs too in Minecraft terminology.