The warhead is a high L/D design, more than 2. While oblique shockwaves does affect it, it will only reduce speed by a little bit. He's overestimating the effect.
We can tell 'cause the CEP is less than 30 m, it means the warhead can adjust its AoA to counteract its effects.
Btw, its range and speed have been underestimated, the DRDO brochure doesn't do it justice. A 10.2 x 1.2 m, 11.5T two-stage design would mean the release speed would be pretty high. Overall it's a mach 6+ design at impact. To get to an altitude of 100 km with 2 stages, we can estimate that each stage would add 2.5 km/s each to the missile's speed. So 5 km/s is mach 15. To put it in perspective, Agni I has a single stage and achieves a release speed of 2.5 km/s.
With a release speed of mach 15, we could see it stabilizing at anywhere between mach 7-10 and impacting at mach 6-8, but at ranges exceeding what DRDO's claimed. Different trajectories would give it different ranges and speeds.
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