Not really, that is what people think, while forgetting that it comes along with a type system, has two models of method invocations.

And with the introduction of WinRT extensions, it got even richers.

Naturally one can try to call COM via C, and there are some COM APIs that offer C versions of them, however the tooling is already bad enough for .NET and C++ devs, doing it from C only for masochits or people that are religiouly against productive tooling.

IIRC COM relies on vftables being ABI stable so you can pass interface pointers. As long as the interfaces don't pass any non-primitives by value.

It is how I often provide APIs that need to work across (many) compiler boundaries. It is not standardized or anything, but de facto reliable on Windows.