I remember seeing a gif posted here with the commission looking at the numbers and shaking their heads without really doing anything. I believe Canelo is professional enough not to do that but wouldn't be surprised if he could get away with it for the megafight.
the weigh in is just for show. the real weigh in is done before that behind the scenes. im assuming someone from ggg's camp would be there for that but this is boxing so you never know
Not sure about the officials shaking their heads or anything, but he definitely got off of the scale pretty fast and they announced his weight after he stepped off. Golovkin was still standing on the scale when they announced his weight, take it for what it's worth.