It appears that the section is now set in $data, not $opt (and with "section" instead of "Section"), but Display.pm wasn't updated to keep track. This doesn't fix any immediate problems that I can see, but I guess it should be correct anyways.
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Hm, not sure why you think it is passed in in $data. Yes, sometimes "section" is passed in $data, but only when that is a variable to be passed to the template, which is distinct from the section to be used for displaying a certain template. Let us know if you see something I don't. :-)