User blog comment:Ghmorello/Chappter 883: My, What Big Dogteeth You Have!/@comment-24850639-20171027153711/@comment-24850639-20171027182938

As in while he's using this method for bypassing armament, it forces him to cut back on his observation? That would make sense to me, since Gear 4 was stated to be Luffy "overusing" his haki. We never got much of an elaboration on what that means.