That tweet is fake, and as repeatedly stated by Microsoft engineers, the start menu is written in C# of course, the only part using React native is a promotion widget within the start menu. While even that is a strange move, all the rest is just FUD spread via social media.
It is funny how quickly this became normalized. During Vista time everyone was absolutely shitting on awful performance, now that PCs became faster it is apparently fine to use one dog ass slow managed language (C#) over another (JS with RN).
Even though RN for Windows is just a thin wrapper over WinRT, but who gives a shit, right? Because JSLOLLOLOL.
