Because there is no licensing issue because this project hasn't been released. This blog post is a preannouncement. When it's released and its known what license it uses then it will become a pertinent discussion.
That line of reasoning could be applied to pretty much every single comment in this thread. Literally. Pick any comment and you could simply respond with: "Well it's not released yet so it's not pertinent".
The very fact that the announcement includes "the ultimate goal of contributing it to the open source community later in 2017" makes the licensing issue pertinent, particularly given Facebook's licensing history.
