I do not know if it would be centralized but it would be an extra addition to the crypto space and I believe it will spread the word faster than the existing process. Facebook coin would gain big value in future if it is introduced in the market because like BNB-backed by Binance, Facebook coin will be backed by Facebook and might have good demand.
all still depend on what Facebook coins will be used for. there is a possibility that there will be some additional features for people who work on Facebook like game players who broadcast live on Facebook. because they might get money from Facebook coins and advertisements.