When I was training a lot I regularly did 20 rounds in 5 seconds, all in the "A" zone at 5 yards. That was from low ready, not from the holster.
Again, the speed itself (20 rounds in 5 seconds is a 0.25 split) isn't the impressive part, it's the combination of speed, movement, and a 4 inch group that made me incredulous. On the other hand, I find nothing unusual or unbelievable about your statement of 20 rounds in 5 seconds all in the A zone (I assume you mean an IPSC target). Instead of the aforementioned 4 square inch group/target, the A zone on an IPSC target is 6 inches wide and 11.02 inches tall, and at five yards from the low ready with no movement, well suffice to say that I'd be disappointed if all the hits weren't in the a-zone. In fact, had Matt said "all hits in the a-zone" I wouldn't have even responded to the thread, because that level of accuracy doesn't stretch the imagination.
To explain it another way - the "X-ring" on a standard NRA Action Pistol target is 4 inches in diameter. The 10 ring is 8 inches, and the 8 ring is 12 inches in diameter. I have seen top level professionals miss the 4 inch x-ring from 10 yards away, while standing stock still using the finest custom guns money can buy, which is why when matt says "a fist sized group" while moving at 7 yards away and shooting 11 rounds in 3 seconds, I am incredulous to say the least.
But 20 rounds at five yards into an IPSC A-zone in 5 seconds? That I believe, because as claims of speed and accuracy go, it's not outlandish or unusual.
Now, what this post doesn't mean is that I think what matt claimed is impossible or that he/his students can't do it - as I've maintained this whole time, just because I'm a disbeliever doesn't mean I can't be converted, it just means I'd have to see it to believe it.