If Facebook has shown anything, it's that React's licensing is fluid and cannot be relied upon long-term. It's one thing today, it'll be another next week. Next year, who knows? Once they change the license, they'll become a flip flopper. The precedent will have already been set for them to do it again in the future when this framework wars blow over / die down substantially.

Facebook doesn't care about anyone's project but they also don't want to lose mindshare either. I would expect them to change the license again in the future when it will be much harder for projects (read - there is much more technical debt ) to make the call to switch frameworks.

Whatever framework Gutenberg chooses though regardless of the proposed agnostic approach or not should become part of the WordPress development guidelines. Then there is at least a standard set in writing. It can be followed or not. If not set, it will be more wild west chaos which will ultimately not benefit or better the community going forward.