This is literally what teachers do.
They have to make it seem like every misbehaviour is new and shocking because if they just went “damn son that’s nothing, when I was your age I jumped off the school roof and yelled fuck all the way down” it would be impossible to give them detention for throwing a pen across the room.
I was once in a lesson during my teacher training where a kid left a drawing of a dick on the teacher’s chair and she acted like the kid had killed her puppy in front of her. After the lesson we both laughed our asses off about it, she wasn’t insulted in the least, it just wasn’t acceptable behaviour.
Tl;dr Minerva is being a great teacher, and she’s probably got a poll going with the other staff at Hogwarts as to what crazy shit Harry and Co. will do next.