Thanks, Scorpius. I'd parsed it as only one element being contained, which led to something analogous to the Ximenes example of "I am in the plot" = PLAIN. No doubt you're right and both elements are, as you aptly put it, notionally contained, but like you I'm not keen on containers where one end is completely missing. Plural verbs for multiple fodder are something of a moot point. My own view FWIW is that it's arguably correct but also inelegant to follow "X Y" or X,Y" with a plural verb, as it doesn't make much sense as English (you wouldn't say "birds, insects fly" for example). The issue can be resolved with a conjunction like "and" between the elements.
I withdraw my objection of unsoundness but it's still not the best clue I've seen.
I seem to be dominating this thread so I hope there will be some more contributions from the good folk who hang around here!