Putting aside the fact that Windows RT was a commercial failure and discontinued which makes it weird to push yet another effort that this would be anything more than some niche demo thing like Raspberry Pi support, Windows in of itself is not what concerned potential Mac switchers.

People are concerned that they have some mission-critical, unreplaceable app that only runs on Windows, that has no acceptable Mac analog (doesn't exist, doesn't have feature parity, data formats are incompatible).

Windows on ARM doesn't solve anything because almost no Windows apps that people care about were ever ported to Windows RT. (It was probably more likely there was a Mac port.)

Windows 10 IoT Core is already running on ARM and it runs UWP apps: https://developer.microsoft.com/en-us/windows/iot/explore/de...