How can it "capture" the calls without knowing what it's capturing? It has to know that there's a windows API function called "CreateWindowEx" that takes particular parameters, otherwise how could it possibly "translate" it? And the fact that CreateWindowEx takes particular parameters is precisely the API.
Of course the implementation of that API will be different in WINE, just as Google's implementations of the Java API are different from Sun's (aside from the 9-line rangeCheck which is a separate issue). In fact it would be fair to describe what Android does as "capture the API calls and transform them into a different Dalvik API call that ends up performing the same function".
So... you're saying it needs to implement the Windows API? If APIs are copyrightable, then that's a violation of Microsoft's copyright. You've included a copy of Windows' API in WINE.
Copying APIs is strictly necessary for interoperability. Allowing APIs to be copyrightable encourages monopolies by legally prohibiting newcomers' software from being compatible with their competition.
It'd be like if Microsoft were allowed to sue Google Docs and Libreoffice for making their software able to open Word documents. (Except in this case the "documents" are source code.)