Every company can use the blockchain technology but that does not mean that they need to create a coin that is being traded in any exchange, it can be a private blockchain project rather than a public one. I do not think so that facebook will start a new crypto, but they might integrate the blockchain technology at some capacity. What is the real use of every company starting their own coin.
Yes, after all, I have not found a good reason for Facebook to make their own cryptocurrency? Is it to reward every viral post? Just kidding. Well, your explanation of the possibility of Facebook adapting blockchain to their system makes more sense. There are many things that can be done with blockchain, not just about cryptocurrency.