FTA:

"With victory in sight but not yet in hand, it would be mighty tempting for Russia to launch a nuclear-armed missile on a secondary Ukrainian city and demand Ukraine’s immediate and unconditional surrender or else another major city would be next. Continued resistance from Kyiv would be suddenly rendered foolhardy, if not suicidal. In this scenario, the Kremlin could terminate the war more quickly, with fewer casualties, and on conditions favorable to Russia."

He has the end of World War II in mind. But the key difference is that in WW II, the US was the only nuclear power. Nobody was around to say "Absolutely do not use a nuclear bomb, and we will consider it a global threat if you do."

Russia seems content to grind its way through the war. If they were to find themselves with the upper hand, I suspect they'll continue to throw bodies into the meat grinder. They simply don't seem to care about coming out of this with fewer casualties.

I suppose nothing is impossible. This entire war is absurd, so nothing is off the table. But I don't think this scenario is likely.