Tell me you never used those APIs, without telling me.

No they don't work, that is why each iteraction requires a rewrite.

WinRT for Windows 10, isn't the same as WinRT for Windows 8.1, isn't the same as WinRT for Windows 8.

WinUI 3.0 has features that are Windows 11 only, although Project Reunion promised compatibility across Windows 10 and 11, it is still quite far from Win 2.0 in features and tooling, years away in fact.

Likewise the WinRT used by WinUI 3.0 in Win32 mode, isn't the same as WinRT used by WinUI 2.0 in UWP mode. Meaning the set of underlying COM plumbing differs in behaviour and exposed set of interfaces.

And I will leave it here, as Github issues and discussions already have plenty of rant material on the matter from the Windows developer community.