Arteta says weird shit all the time, a lot of managers do. I doubt the board buys any major player without Arteta's say approval, such is the influence he'll have.
I don't think anyone thought Havertz would be able to be bought and dropped into a position he's rarely played for ages, with a new team after 3 training sessions and just nail it straight away.
I know fans don't have a lot of it just now but we might just have to be patient with him. Don't think anyone is denying it's a bit of a gamble considering his last couple of seasons, but let's not write him off after 45mins of pre season.