score:2
Pigneto station is fully open and operational, and so is line C from San Giovanni to Monte Compatri/Pantano (and not only on Wikipedia, but also in real life).
I know that personal experience and personally often using that station is not a formal source, but I wonder what I can do more. Taking some photographs there, perhaps? A confirmation comes from the official website of Rome transports, which gives the timetables and other information for line C.
Upvote:3
According to Wikipedia line C is open, and as of May 2018 it is no longer unconnected from lines A & B since there is now transfer to line A at San Giovanni station.
So you're probably OK.