Thats a bug. Its not clear where from but I intend to find out.

/me adjusts his glasses.

Er, not a bug. :-)

Anyway, the point I was originally going to make was that the xml view is per node and is escaped. So the "scroll to the top and hit the xml link" is going to do different things depending on whether it was being viewed as part of a thread or as the root node. When viewed as the root node it does "the right thing". Whether that is what you expected I can't say.