I am not suggesting that "hospital ship" requires a certain size or dedication to medical capabilities. My point is rather that the term itself is just a catch all for a wide variety of medical support capability and as such not a lot better than eg "cargo ship".Even then, I think the tweet is a bit odd as it seems to suggest that hospital ships (or rather medical ships) need to be a certain size to qualify as such, and that if they're smaller then they would somehow be more.... Multirole and less focused on the primary medical mission?
For the same reason I regularly qualify as to what the US ships are really designed to do vs eg Peace Ark. But Twitter type limits and all.
PS: "Medical support ship" I guess in that regard is a far better term.