Problem when Generating an XML from VF page using ContentType

I'm attempting to retrieve XML from a VF page, but I'm not receiving XML, only some javascript.

I have a simple page:

<?xml version="1.0" encoding="UTF-8"?><apex:page contentType="application/xml">
<result>
{!$CurrentPage.parameters.ResultString}
</result>
</apex:page>

with being redirected to by the result of a different controller:

ResultString = '<reason>' + NewProspectStatus + '</reason>';
if(NewProspectStatus.startsWith('New Lead: '))
{
	ResultString = '<code>0</code>\n<description>SUCCESS</description>\n' + ResultString;
}
else
{
	ResultString = '<code>1</code>\n<description>ERROR</description>\n' + ResultString;
}
system.debug('ResultsString: ' + ResultString);
Pagereference pr = Page.ELeadThankYou;       
pr.getParameters().put('ResultString', ResultString);
pr.setRedirect(true);
system.debug('Response: ' + pr.getContent().toString());
return pr;

But the result looks like this:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <meta HTTP-EQUIV="PRAGMA" CONTENT="NO-CACHE">
<script>
var escapedHash = '';
var url = '/eleadthankyou?ResultString=%3Ccode%3E0%3C%2Fcode%3E%0A%3Cdescription%3ESUCCESS%3C%2Fdescription%3E%0A%3Creason%3ENew+Lead%3A+Buddy+Dwight+imported+from+Lead+Provider%3A+FromORG2%3C%2Freason%3E';
if (window.location.hash) {
   escapedHash = '%23' + window.location.hash.slice(1);
}
if (window.location.replace){ 
window.location.replace(url + escapedHash);
} else {;
window.location.href = url + escapedHash;
} 
</script>
</head>
</html>

I've read through this post

Generating an XML from VF page using ContentType

Which is a nice intro to what I'm attempting.

Any idea why this is not returning XML?