When the linker detects that a ComImport method is not being used, it removes them from the interface. This is not correct: all ComImport interface methods are implicitly used, because they are used to determine the native vtable layout.

When Roslyn embeds interface definitions from interop dlls, it replaces unused member with void () placeholders: https://github.com/dotnet/roslyn/blob/e704ca635bd6de70a0250e34c4567c7a28fa9f6d/src/Compilers/Core/Portable/MetadataReader/ModuleExtensions.cs#L193

Using a placeholder like that can unroot types used by the parameters/return values, so it can still help with further size reductions; but the methods cannot be removed entirely.