Thanks for clarifying. I agree. SD has been a great value, and I have no problem spending $30 to get it going on M1. In fact, I do have an M1 MB Air already, so now that it's running properly, I might as well finally go with that.They explain it in their blog. They have legacy code problem with their licensing system. You can’t upgrade from Intel-version to M1-version on a pre-2019 license.
You can run SuperDuper in Rosetta if you have the older license and don’t want to pay for an upgrade.
I’ve gotten so much value out of $30 paid years ago, I have no heartburn about buying anew for M1 hardware.