Yes a really fast acceleration, impressive. But as little piston already said, it is 3,5 - 4 sec. And that is fast for a jet engine! Nobodody needs faster, and hardly any turbine in the world can do much faster than this. You can clearly see it in the video. At 3:29/3:30 he throws the throttle to max, and around 3:33 it reaches full power.
As on every turbine the first 15 to 20K is the hardest and take most of the time. From 55/60K to max it will be only 1,5 sec or even less.