That is an interesting point.
From what little I know, there is often no shock wave generated from the impact of a dud on the ground. But if you see the pictures and videos, there are shattered windows on buildings, and destroyed walls and structures as well.
Moreover, the impact crater itself, and the lack of any debris WITHIN the crater itself also tells that there might have been a explosion.
But then again, the motor section is pretty nearby.
Here is an impact of a demo missile btw,
In the end though, I think it would be pretty easy for forensics to know whether there were any explosives or not. And I do believe the DG ISPR did have some reason to say that there were no explosives on board.
It is a mystery!