I'd guess it's unlikely to be the real use case. The real one is classified. Plus it's not like more deadly nuclear weapons would change anything, we can do bad enough with what we already have.
> it's unlikely to be the real use case. The real one is classified.
What are you basing this on?
> it's not like more deadly nuclear weapons would change anything
We haven't been chasing yield in nuclear weapons since the 60s.
Our oldest warheads date from the 60s [1]. For obvious reasons, the experimental track record on half-century old pits is scarce. We don't know if novel physics or chemistry is going on in there, and we don't want to be the second ones to find out.