Guy was kind of a poo for showing it blow, promising to share, and then it was just a cockerel tease.
I don't think it's thermite, because of the speed of the reaction, my guess is gunpowder, but when other kids were making hairspray flamethrowers I was playing nintendo.
If the guy actually felt like he made a mistake posting the original video, he'd have removed the original, rather than drop the apology video.
If you ever want to see a laptop burn out, look up hacking with ramzi. It's not particularly technical, I believe he loads the thermite into the laptop with a garden trowel.