A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
OLE implementation in Mac PowerPoint has been improved slightly, but it still comes up short in many ways -- this is one of them :-( Once created, the data displayed in the object will update but in most ways the structure of the object, itself, does not.
IMO, it's better to create the worksheet as a separate Excel file. Make any revisions as needed in that file, then copy/paste a new worksheet object to the slide.