This is (pretty) old stuff. The winerror.h file in the SDK says this:

////////////////////////////////////
//                                //
//     COM Error Codes            //
//                                //
////////////////////////////////////


//
// The return value of COM functions and methods is an HRESULT.
// This is not a handle to anything, but is merely a 32-bit value
// with several fields encoded in the value. The parts of an
// HRESULT are shown below.
//
// Many of the macros and functions below were orginally defined to
// operate on SCODEs. SCODEs are no longer used. The macros are
// still present for compatibility and easy porting of Win16 code.
// Newly written code should use the HRESULT macros and functions.
//

I think it's pretty clear. I would trust the SDK first, and the doc after that.

We can see SCODE is consistently defined like this in WTypesbase.h (in recent SDKs, in older SDKs, I think it was in another file):

typedef LONG SCODE;

So it's really a 32-bit.