The outlook app will be native desktop and mobile (except linux for now).
Plus it will give the maui project more credibility, help grow its userbase. Make the framework better by providing a real world project for the maui team to benchmark, highlighting pain point, provide in-house feedback, feature request.
All the releases that I can think of shunned the standard UI toolkits for their own homegrown UI. Presumably to show the Windows folks that the Office team is it's own little empire.
If you want an identical experience with identical code across the Web, iOS, Android, Windows, Mac, Linux then there is only one solution.
Cross-platform desktop apps, should at least cover Windows, OSX and Linux (appImage/Flatpak) as a baseline. Avalonia works well enough, but MAUI just muddied the waters. With the massive efforts towards web-ui in general, it's really not surprising that many devs/shops are just shrinkwrapping with Electron. Even if there are far lighter options for embedded browser usage of the system's browser engine. In the end, the state of desktop apps sucks all around.