Eh, not sure how the word "Russian" ended up in that comment. It was an American design before it was a Russian one.[1] Plus, there was an added feature in some American plans I've read about (but can't immediately locate) of long-term loitering over adversarial territory and discharge of radioactive material.
What would it matter if it were hypersonic?
[1]https://en.wikipedia.org/wiki/Project_Pluto