It's 100% wrong - this person has a position of responsibility over the 16 year old, whether or he is mature or not.
If this happened to either of my girls or boys, I'd be angry.
Having said that, having been 16 years old and had an opportunity like this presented itself, I would have fucked her too. I'd like to think I wouldn't tell anyone, but that's 45 year old me trying to use logic on a hypothetical situation knowing what I know now. And I know most 16 year olds would too. It's impossible for a 16 year old kid to understand the psychological impact a situation like this could have - we were all walking hard ons at that age, jacking off constantly and trying our damnedest to get laid.
Also young women are dumb.