I think the merit in this article lies more in the techniques that are covered, rather than in the premise that it ultimately failed to prove.
The article does show a couple of good xquery examples in context - how to select a value from a node and incorporate it in a resultset, and how to modify the value of a node.
SELECT Rainfall.value('(/RT/RN[@H=15]/@H)','tinyint') AS Hour
,Rainfall.value('(/RT/RN[@H=15]/@V)','numeric(10,8)') AS Rainfall
UPDATE TP SET Rainfall.modify('replace value of (/RT/RN[@H="20"]/@V) with "8.12345678" ')
All in all, not a bad article, well written and clear explanations, even if in some respects fundamentally flawed!