It's almost certainly unstated US foreign policy on the matter, and not just a media bluff.
They might have thousands but they don't have thousands deployed. Moreover, use with any kind of frequency would just trigger a strategic US response, which would defeat the entire purpose—assuming there was purpose in the first place, which there isn't given conventional cost imposition.
Despite chill messaging, I suspect the US's strategic trigger finger is far itchier when things get real, and Russia knows this. Their triad has two arms which very possibly are entirely negated, and their C&C infra is garbage. There's a very real risk they'd just straight up die and accomplish nothing.
All that said I do agree that this would result in mutual mass strikes with strategic weapons, and whatever tactical weapons may be appropriate for such a strike. This is why I think direct conflict with Russia, or Russia using nuclear weapons of any sort in Ukraine, is likely to escalate rapidly to what would be the defacto end of the world.
[1] - https://en.wikipedia.org/wiki/Russia_and_weapons_of_mass_des...
>There is no concept of deployment for these - it's simple and normal usage.
They are absolutely deployed and accounted for.
>...and thousands of tactical nukes of all shapes and sizes.
Most sit in storage, not deployed.
>But speaking of a deployed tactical nuke is somewhat nonsensical.
The people whose job it is to track deployments of tactical nuclear weapons would probably disagree.
But strategic nukes are a different beast those simply because of their size and requirement for specialized launchers, as well as their relative incongruence with conventional weapons delivery devices. You're not launching a strategic nuke out of a conventional rocket system (as could be the case for a tactical nuke) for sure! So this makes them, more or less, able to be reasonably estimated. It's still a pretty big guessing game, but it's generally going to be at least roughly in the right ballpark.
The bombs that destroyed Hiroshima and Nagasaki, to several times larger, would generally be considered "tactical" in modern times. These are massive weapons. Then there's ADM/'nuclear landmines' [1], and more. In the absolute worst case scenario, there's even the possibility of transitioning to strategic weapons. Approaching this sort of battlefield with conventional forces is not a viable idea.
So I have no idea what the US will do if Russia resorts to nuclear usage in Ukraine, but I think this scenario can logically be discarded as one of the possible options. It plays well in the media, but it simply does not make any strategic nor logical sense.
[1] - https://en.wikipedia.org/wiki/Atomic_demolition_munition