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Well, I assume you mean using the throw from the demon flip. It’s not a cancel. While in the demon flip, if you press the throw command (lk+lp) while touching the head of your opponent (or thereabouts), you’ll flip over 'em and give 'em a toss. If you don’t mean using the demon flip throw, the only other thing I could thing of is doing an empty-dive into throw. To do that, just aim a dive kick out of a demon flip to where you JUST miss your opponent, then give 'em a toss. You can’t “cancel” the flip itself into a throw, though.
i don’t know if this is what you guys are talking about, but i’ve seen Japanese Akuma players do the flip and hit kick really, really late so Akuma makes the grunt he does when he dive kicks, but it comes out so late that it doesn’t look like it came out at all. they usually do this in front or behind their opponents (at around kara-throw range, it looks like).
That’s the second thing I mentioned. 
It’s just hard to describe. But yeah, most people will see that coming, but it’s yet another thing you can add into your mixups with akuma to keep your opponent on their toes.
I can do it just press kick late ish as hes descending and he will land clean on his feet and and you can kara throw their ass. And Yes Japs do it alot.