Note the negative formulation. I'd suggest that the way to 'get' it is, "There is nothing WRONG with this, but that doesn't mean there's anything RIGHT with it, either." And often in recent years an explanation more or less to that effect is appended to the imprimatur.
Further, while it could be free from error in matters of doctrine and morals, that certainly doesn't mean it's free from error in matters of fact, or even of "vibe".
I guess debating whether or not someone who may or may not have existed was a nun makes me want to get out my knotted cord and count the angels on a nearby pin.