https://bugs.winehq.org/show_bug.cgi?id=39002
--- Comment #3 from Matthias-Christian Ott ott@mirix.org --- I have an internal application that sets this property and fails with an error because ISAXXMLParser returns E_NOTIMPL. Unfortunately, this application is an internal application and I can't share it. I only test it with Wine and the production environment is Microsoft Windows.
I can provide a minimal test case if necessary. But I think you can construct an XML document which is not encoded in Unicode and the heuristics will fail. An application should be able to set the encoding based on external information (see appendix section F.2 of the XML 1.0 Recommendation). So an application would set the charset property of ISAXXML to the appropriate encoding for the document.