The notes aren't very high. He's just singing with a very bright voice.
Brightness and highness doesn't have to be related. For example, listen to Bad from ZooTV Dublin: the first wide awakes are in falsetto, the second ones are in full voice. Both are still the same notes.
Yes, its obvious you know a lot about it But I'm not really a singer myself so it doesn't tells me a lot. But thanks for the explanation Your a singer yourself right?