Full disclosure: I have not had a problem with this.

It's just a theory I have that this is low-hanging fruit to reduce C++ binary size.

You're less likely to define the same structure and methods of a type in exactly the same way as someone else in C because we don't have the STL (ofc). So it's probably a worse issue in C having a hundred different implementations of a linked list or some array type across your system in each program.

I just think there's an opportunity to aggressively dedupe object code for "representation-identical" types in C++.