Probably "wrong" here should be in scare quotes. It's not the wrong year; it does return the correct ISO year. It's just that ISO year is not what you want so you should be using %y rather than %g.
I'm assuming that (1) the poster is warning others about this or (2) he finds it amusing that the response to "The year is wrong" is (roughly) "No, that's how the standard defines year. The output is right relative to that standard. Dates and times suck." (the last sentence is implied) or (3) both.