Yea that's what it was.Didn't mad eye give him a herbology book or some shyt which contained that plant which allows harry to breathe under water?
My problem still is that dude seemed like he had been teaching for 10 years when it was actually some evil death eater dude, like just the way he bantered with some of the students. I agree he had the ulterior motive with Neville, but whoever that death eater was he was a HELL of an actor considering he imitated professor mad eye so flawlessly
and I get what you're saying, but I believe this was Moody's first appearance to everyone in the school and the only people who could have called him out was Dumbledore and the other professors who knew him. The students wouldn't know shyt. I remember they mentioned that he was extremely paranoid which is due to the death eater being scared of being caught, but Moody was apparently already a paranoid person before so they just accepted it. As far as him knowing how to teach and picking up his mannerisms, I guess he's just a hell of an actor lol.