I think meta and facebook before it have always valued a very high standard of engineering, and have also been generally pretty good about open sourcing a lot of that work in a way that allows a lot of people to work with their tools. This doesn’t seem all that out of character.
It's a huge company with a lot of different voices. One may create react and open source it while another would add a clause that if you sue facebook over anything your react license disappears. When they are good they are really good.
