Hello MastanKhan
This data was from the wikipedia.
Not just the distortion in the canopy, there are many other things that come down broken or damaged, but its not like the plane is gonna fall off the sky, thats highly unlikely.
Point is that it can fly past Mach 2 if needed.
First off the JFT's block one speed was 1.6.
JFT Block 2, with increased composites and upgrades and a slight redesign, got 1.8.
And no one is saying the the Block 2 is Mach 2.
People are saying that Block 3 will be Mach 2, perhaps the design will be tweaked again.