The latest Windows 11 preview build in the Beta Channel delivers a rather odd change to the Start menu. For some reason, the "Sign out" button is hidden behind a Microsoft 365 ad and other banners.
New features get released into the developer preview. It's basically beta test windows. It's what the tech sites watch to see what new features/etc have been added/removed/changed. Usually they end up making it into the release builds, but sometimes they end up not doing it, or the change doesn't apply to certain regions.