It is based on the same ideas as C++/WinRT, which I am still bitter about, because it represents a productivity drop versus C++/CX as the ones pushing for it are hoping that ISO C++23 eventually gets the features that enables the VS tooling with C++/CX today.
So you are back to manually copying files around and writing IDL files with Notepad like experience as if using ATL style development in 2020.
Most likely C#/WinRT seems to follow the same fate in productivity drop.
https://github.com/dotnet/runtime/issues/35318
coreclr.dll is currently half a megabyte smaller than the 3.1 release.