I think GP was taking about the general nature of “previously assumed to be unbreakable” methods being broken. Not sure if he has implying using a checksum also for encryption
What do you mean by "previously assumed to be unbreakable" ? SHA-1 has been known to be unsafe for a dozen years, we just went from "assumed to be breakable" to "yep, definitely breakable, here's how one exact attack will work".
I can see why backups might be needed for a dozen years, and I can see why encrypted backups might be needed, but outside plainly fake requirements like those of "national security" why would encrypted backups be needed for a dozen years? Aren't we throwing everything sensitive away after seven years? After that isn't it mostly about preserving history? Even things like balance sheets that might be sensitive today will be too out-of-date to be sensitive a dozen years from now.
The obvious counter-example is my library, however old my photos or music or videos are I'd like to keep them for as long as possible, and because they're private I'd like to keep them in an encrypted form