Yeah, well, sometimes a change to the install process that shouldn't have any effect on anything else...does.
Beta 3 gave an error when using bless to bless the drive. The underlying issue was code we have that needs to ignore certain types of output on stderr that aren't actually errors. (For example, the EFI fix that I describe in this blog post produces an error that isn't actually an error–we know it's going to fail in a specific way).
The unexpected part is that just before the beta, we made a change to the installer to try to improve our workaround for systems that required rebooting post-install to make Full Disk Access work. After we made the change, we didn't re-run the full suite of tests because we (incorrectly) thought the change was isolated to the install process.
However, it was made in a runtime element that was shared with the way we executed bless. We didn't take that into account, and should have re-run all the tests.
The backups themselves are fine (and are even bootable, even though there's an error issued). Beta 4 fixes the false error indication: once installed, bless will not give a false failure.
Sorry about that. Beta. >sigh<
