I thought the download was to add additional content to the Library. - I see now that it was just to correct a problem where there was no content.
My Library already had content, so apparently I fixed a problem I didn't actually have.
You added the first content when you "downloaded the Encore CS6 Functional Content and installed it." That installed only templates (full menus with backgrounds, buttons, etc). By the way, other than whether there are motion backgrounds included, all that is in a single PSD.
But you had only a relatively small number of templates, and no separate files with just extra backgrounds, buttons, etc.