That’s been covered some already, primarily for damage assessment, but it can also be used to test repair.
There’s recently even a more authoritative confirmation that you have a couple of ways to test file integrity:
Question about TEST command vs. Backup with –full-remote-verification and backup-test-samples
So basically either the test command or a backup with high --backup-test-samples should see if things are present as Duplicati thinks they should be. Maybe a repair with --dry-run to make sure it picks nothing up.
Ultimately, self-tests are no substitute for an actual test restore from the backup, to make sure it seems OK.
As an unrelated note, make sure you don’t have any full disks, in case that might have truncated some file, however with multiple reports from different people, I suspect something went wrong at Wasabi at that time.
Running a log at at least Information level might have been handy to see if the uploads showed any issues. This is what Backblaze B2 gave me yesterday on a backend test. Maybe B2, maybe Internet. Hard to know.