The only difference, according to my understanding, is that it is harder for an anti-ballistic missile system to defend against a hypersonic missile, due to its speed and, I think, ability to manoeuvre in flight. But as far as MAD goes, I think you're right: it makes no difference.
What may also be important is that Putin's ability to assemble many of these is likely to be hamstrung by the embargo on supplying sensitive micro-electronic components to Russia. There are already accounts from Ukraine of Russian missiles containing repurposed microprocessors out of washing machines.