Because the file that you think is the same file may not actually be the same file.
It's alphabetical order, but not in the obvious way.
For conditionally enabling features, say.
Subtlety is not its strong point.
void* __cdecl winrt_make_YourNamespace_YourClass(void) "?
You enabled optimizations, but there's some extra bookkeeping to support those optimizations.
winrt::impl::produce<D, I>‘: cannot instantiate abstract class, missing method GetBindingConnector
The header file requirement was always present, but you often got away with omitting it. Not so much any more.
It's still there, but you have to dig a little deeper for it.
A nice parlor trick, if you had the memory for it.
Which token did you adjust?
Narrowing down the source of the missing header file.