This week's MJCast roundtable on the Cascio tracks was really interesting. The suspicion is the Cascios brought Brawley in to make it sound more like MJ with adlibs as that was his expertise in making MJ sound like MJ in Invincible. Something like that.
They explain it better on the podcast
But if Cascio gave the estate tracks covered in adlibs and weird edits, why didn't it ring alarm bells right away? It's so bizarre.
There's a a podcast coming soon called "Faking Michael" that apparently will go more into it. They mentioned it on the roundtable too.
EDIT: The roundtable also shouted out this two part deep dive into the Michael album. It's pretty great at recapping everything...