Jerry Pournelle thought up the concept, but he'd most certainly read the "Doc".
The ones mooted for use by the USAF were 11.5 ton TNT equivalent, but would have a mass of 8 tons. Impact speed was Mach 10. A conventional bomb could do as much damage for less cost as the article points out.
A city rather than bunker buster would have to mass many tens of thousands if not millions of tons -- as the Chelyabinsk meteor demonstrated. It would take project Orion to heft that much stuff around so why no just use the nukes themselves.