Now that was a proper reply.
I stand corrected. I didn't take into account the fact the the nuclear assembly can't take the g force of conventional explosives. I guess this would allow conventional bunker busters to penetrate a lot deeper. If the access tunnels could be located and a smaller nuclear bunker buster detonated near them, then they could be sealed up entombing the occupants. Better yet, if the explosive force traveled down along the tunnel, and incinerated much of the inside (like a thermobaric weapon) before collapsing the tunnels.