I think the coolest thing about this is you avoid so many round trips to the server. Every single database call and asset request happens on the client! (After you accept the several seconds of loading time.) I think it's also hilarious, because WordPress is probably the most-used MPA solution out there, but this basically turns it into an SPA. And it performs even better than most SPAs, because it doesn't need to do API requests to a server constantly.

I also think the SPA parts of this (the post/page and site editors are very complex React applications) feel snappier in this demo than they do on my local dev environment. Really shows how good SPAs can be when you cut out server round trips.

Disclaimer: I work for Automattic, and this has been a super cool experiment to watch.