Having a centralized token and calling it money is a different thing altogether, they are looking for a stable coin and still i am not sure how they will convince all the major nations to get it legalized, BTCitcoin on the other hand is  a decentralized currency and no government can ban it completely and that is not the case with centralized coins. If a government does not want their citizens to use them they will ban them and since facebook is their main working model they will not risk getting that banned too.