Anyone watch motoGP? Sometimes they have onboard video with lean/throttle/brake overlay.
I watch those very carefully, never once seen an overlap between braking and throttle. Not even when Rossi rides (because there are rumors he applies this technique of brakes and gas at the same time)
I have data from Xavi Vierge and he doesn't do it either.
In theory I could understand the concept but the "juice is not worth the squeeze".
It's too distracting, and it could take away from your sensitivity on the brake lever if you are also trying to apply 5% throttle.
If you are not at the limit, and not going fast, you don't need sensitivity on the brake lever because you won't be using it anyway at high lean angles right?
So when you get faster, you will find yourself with some light brakes at 48 deg lean, and if you press just a tiny bit more on the lever, your front end will close.