In the parent's defense, the rest of that paragraph and the chart below it downplay Microsoft's role in favor of Google's, which could be viewed as "not quite right".
Indeed, myself and others were doing [A]VBAX apps in IE before the term "AJAX" hit the mainstream. Not always async, and using VBScript in the browser instead of Javascript, but loading XML from the server and doing XSLT to build the DOM. It actually was pretty nice, at the time. IE5. You couldn't do things like that in any other browser for years.
That's not quite right. Microsoft invented XMLHTTP, the interface which XHR is based on, in '98 or '99 for Outlook Web Access.