How Facebook chooses to license its products is a matter for Facebook.

Which software Automattic chooses to use is a matter for Automattic.

Which software gets bundled with distributed WordPress (i.e. from wordpress.org) is subject to the trusteeship of the WordPress Foundation.

So what has the Foundation to say about the potential bundling of React with WordPress? Its current silence looks like a dereliction of duty.

Has it taken legal advice? If so, what did that advice say? If not, why not?

Maybe Facebook will decide to change the terms of the React license and render all this moot. If not, and React gets bundled with self-hosted WordPress, I wouldn't be at all surprised to see someone take legal action against the WordPress Foundation for breach of trust.