The whole value proposition comes from laying a ginned-up guilt trip on people who are vulnerable to shaming, and then holding out the hope of a get-out-of-jail-free card. It backfires on them in the edge cases, of course.

The flip side that you mention is based on the verse that says that "all our righteousness is as filthy rags" (literally, if you dig into the etymology of the original greek, menstrual rags) so far as god is concerned. Only by appropriating god's righteousness as your own in the approved manner can you be guilt-free.

Yes, it's quite the franchise.