Call me a fearful fool, then, but speaking as somebody who spent the first decade of his life listening to the Saturday morning bomb shelter siren test, I take this pretty seriously.
There's no way to know for sure, but my personal model of what's happening is that Putin has ceased to be rational. I'm thinking something happened medically, like a stroke. That it's impacted his executive function, but not enough to be flagged in the superficial conversations he has with nonmedical subordinates.
This isn't advice to give Putin anything he wants, but rather, a preference to not provoke a nuclear exchange, because for the first time in 60 years, I think there's the highest possibility that it could happen.
NATO has several policies for dealing with nuclear exchanges, one of which is Proportionate Deterrence, or Flexible Response. It's not all MAD. But that's still just for attacks on member states, and *very* unpopular in Europe. Specifically, because that would be the most likely location of the detonations, and fallout would contaminate neighbours. I don't think retaliation is desirable in this Ukraine situation.
A 20kT Proportionate Deterrence against, say, a Russian battle group advancing on Kyiv from the North, would contaminate Kyiv and kill thousands of civilians. Worse: fallout would probably spread into Russia and it's possible they could consider it a Western escalation onto their own territory and retaliate in kind into Western Europe. I just don't see any value in threatening to use tacticals against the Russians on Ukrainian soil at this time, and advice against even threatening.