Does a foxhole protect from the overpressure blast of a nuclear explosion? With fragmentation grades, you're getting behind cover that will absorb the shards before they hit you--cover can't do anything about a wave of pressure.
On the other hand, we're only taking about 10-20 tons, not kilo-tons, of yield, so in pressure it's more like a Daisy Cutter or MOAB, or something smaller that hit close, and there's lots of experience of that. It might well be preferable to being overrun by a unit of the Red Army in the next few minutes, but, obviously, selecting a target at > 1,000 meters would be a good idea.
My general point, though, it that this weapon is held to be axiomatically "crazy", when it's not in the context for which it was designed and fielded.