It is within the context of the root-window, yes. For readability purposes, assuming my_xtermwindow is a window title, then quoting it would probably jelp, but shouldn’t affect things. That said, it should still work. Is it the case that it isn’t for you?
If there is no window named my_xtermwindow, it opens a new one, however, whenever it is opened, it is not closed, which means that the rc for the command Any is Match, but the close command fails, since it applies to the root window. I guess it is not what manpage authors intended to do.
I see. If a window is open, the condition matches, but the context is not that window, instead it is the root window. The real question is if this is a bug in the Any command, or is it a typological error in the man page.
If the keyword Any is replaced with All, it does what I think they are trying to do in the man page.