It would be pretty weird if SMS were available but not data.

No it wouldn't. SMS is actually a control message on the voice stream (my words might not be precise). You can send SMS with no data connectivity.

I meant in this particular case it would be weird, because it would mean that the perpetrators are somehow blocking mobile data but neglected to block SMS.

Right, and there are ways you can consider the validity of either method, but to block SMS would mean blocking voice.

Perhaps a temporary data hiccup might be a more realistic solution (or simulation, if malicious) versus "Call cannot be connected".

I think a state actor could filter at will, since they could MITM the connection and pass stuff through selectively. Not that I can see why they would bother. Although I can't see why they would take this action at all, which is why I don't believe the story in the first place.

Pretty much, agreed.