He did say it was 3.8, I think, 44 notes I think. But he said that, in the 90s, Michael's range expanded, due to age, to 4 octaves. He retained his highest notes while gaining lower notes at the same time.
I think on "Earth Song", certain parts near the climax, when Michael sings very high, before the "what about us" refrrain, those are in full voice, I think. Though I'm not an expert, so I don't know for sure. But it sounds like it's in full voice to me, when he sings "Haheeahah". And the parts when he sings "Ahahahaheeah", etc... And also, on "Cheater", when the chorus comes up and he sings "Cheater" underneith the layered vocals, that's very high and in full voice too, I'm sure. But yeah, like you said, the way Michael controls his voice while changing registers is astounding. It's so smooth and unditectable. He's a consumate professional.