The other problem is air resistance increases faster than speed. For horizontal flying, lower altitude hyper sonic weapons, once they run out of fuel, they are going to slow down much faster than other weapons. Marketing hype is not physics, and physics always beats marketing.
Kinzhal's impact weight after running out of fuel is 2,000 lbs with a 500 lb warhead. The MOAB is a bomb, not a missile. It's impact weight is 21,600 lbs with 18,600 lbs explosive filler. There is no way the Kinzhal with 1/10 the impact weight causes damage over twice as deep as a MOAB.
My guess would be that the Kinzhal does not run out of fuel prior to impact.