C ABI is more than how ints and array of ints sit next to each other in memory.

It cares about calling conventions and what you can store in registers vs what you cannot. There are multiple possible ways of doing an RPC call and C ABI only provides one way of doing it.

COM, WinRT, XPC, AIDL.

Now you can move the goal posts and assert that any data serialized into a memory buffer is an array of ints.