I don't think this statue is porn but I can understand why it could break Facebook's rules. Context is important. A photograph of a naked woman in a biology textbook isn't porn, but if you upload exactly the same picture to Pornhub it becomes pornographic. A statue of a naked woman in a museum clearly isn't porn, but that doesn't mean it can't be regarded as porn if you upload a picture of it to Facebook.

I think in Facebook's case, it's important to ignore context, lest they get drawn into the awkward position of saying what is art and what isn't.