The check that earned its keep for us was comparing rendered digits back against the copy sheet, because the expensive defect is not a wrong label, it is a truncated one. A figure clipped to fit still renders as a perfectly plausible figure, so every check shaped like "did the text appear" passes while the number is quietly wrong.

Found that when a card went out with a count missing its last digit and nothing anywhere flagged it. Your point about checks that can actually fail is the whole game.