AFAIK the Start Menu itself is still C++ and XAML however only the Recommended section is build with React Native [1].
Funnily or rather sadly, they seem to be quite proud of using it as seen in the video.
It’s been this way for over a decade. The year of the Linux desktop was 2009; the world is only just catching up.
Yeah, that’s a misconfigured system. I bet you can fuck up Linux enough to get a similar experience.
I’ve always been using Windows and the only time I ever had to wait that long was around the Win98 times on slow hardware.
After login, I can instantly use everything on Win 11, and the only delay is a bunch of apps starting (that I chose to start on boot).