That’s part of the strangeness of this whole debate: nobody knows. The list of Facebook’s patents is public, but I’m not aware of anyone publicly going and doing the research to see which of them, if any, are likely to apply to React. (Possibly because of the whole treble damages thing - along with the fact that Facebook has thousands of patents to look through.) Facebook’s lawyers may or may not have done that research, but it’s in their best interest to keep things as vague as possible (at least up to the point where they actually threaten to sue someone), to avoid workarounds.