I suppose one could read the documentation as saying that a variety of issues could occur if the stick were powered only from the TV. I read their disclaimer as saying that the TV might not supply enough power when the TV is on (and thus might not power the stick adequately). If the stick is inserted, and the TV is powered on, and it delivers sufficient current (as listed on the TV and required by the stick), and the stick works, I think it's reasonable for most users to consider that a supported use case.
It would be a pretty slippery argument on Roku's part to claim that the (seemingly unrelated) battery drain problem is caused by the stick not getting sufficient power when the TV is off (i.e. when it is entirely unused). It's fair to read "sufficient continuous power" as pertaining to the state when the TV is on. But I suppose, in a court of law, your point would have merit.
For me, this is just another case of Roku being cagey about the features, capabilities and requirements of their products. (The other one being lack of support for DD transcoding on DD+ sources, which I have already complained about at length in a different thread.) In the meantime, I await a response from Roku about how, or whether, they will address this particular issue.
