He's right. I did some digging and found it.Link
XP was granted upgrade license rights despite requiring a full/fresh install. Only Windows 2000 and older users must buy a full license.
This is still the case even with 8.1 at this time. I can't imagine that XP will still have upgrade rights for too much longer though. 8.1 might be the last OS. Windows XP still dies and loses all support - included security patches - on April 8th, 2014. That day will be a day of many, many future day zero attacks for XP.
In short: nothing to see here, I'm wrong.
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