When you use ODS, you are creating ASCII text files (either CSV, HTML or XML) that Excel knows how to open and render. I see you are using PHTML -- this is an HTML format with very little style (and not an XML format).
The only ways to deliver true, binary Excel files is to use PROC EXPORT or the LIBNAME engine for Excel. You might want to work with Tech Support on this question, because you would NOT use a stored process the way you are -- with ODS.
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