It’s not SwiftUI (which would require Apple’s AppKit or UIKit), but rather interop with the Windows native WinRT https://speakinginswift.substack.com/p/swift-meet-winrt
Well that was until late 2023. Then they realized nobody was writing pure Windows UI code in WinUI 3. (Probably because people were still playing catch up). So they have now have unofficially mothballed WinUI 3 and the new hotness is now MAUI - cross-platform UI! - in 2024. (But no Linux support ho-ho)
Not sure what it will be next year.
Look no further than the Github repos for the general sentiment.