I think for those "Sing this note" pitches, he's not paying attention to the chord played. I think he's getting the pitch from his mind.
That's what seems kind of odd about it. There's a disconnect between the chord being played and him "summoning" the pitch. The chord and him could be in different locations, but he'd be doing the same process.
Not that it's bad. It's just... An oddity maybe with having perfect pitch. Interesting too.
I guess I was expecting him to sing the requested pitch and know how it relates to the chord or have some awareness of that chord in the environment.