Disclosure, that is my Twitter account.
I think these are SAR, basic supply and medical support hulls. Their overall configuration is in line with those roles. The problem is that "hospital ship" is a highly fluid definition including drastically different configs like 919, 920 and the US Mercy and Comfort vessels, which really are massive trauma centres triaging combat casualties in their original role and concept.
I am not suggesting any nefarious use such as for outright military purposes (ammo replenishment etc) but simply that they will probably also see use in establishing and supporting infrastructure on SCS islands etc.
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?
These are some internal pics of the ship class, and it is fairly consistent with a ship providing medical facilities.
(Other articles on the ship when it was commissioned state it has 100 beds, with three OTs, a CT, endoscopy, and services like MH, ORL, ophthal is a pretty legit secondary center level facility)
And the PLAN also has for much of its history operated many smaller medical ships too.
Sometimes you don't need a big tertiary center general hospital, sometimes a secondary center or primary/GP/urgent care clinic is enough, not to mention the considerations of ship readiness/deployability for larger versus smaller ships, etc.
