That post agrees with the documentation that it makes it a deep check. What we needed here was a wide one, and best would be one that doesn’t download all files. See How often does duplicati test your backup archives? although this does hit the limitation that not all storage types can hash for you. See survey info.
I’m glad that FreeNAS had enough tools to do a wide check (however “deep” that check is) of the zip files, however even deeper would be --full-remote-verification if we could get it to do all files, but now I see how:
Should test / verify commands & –backup-test-samples support percentage parameter? had @JonMikelV saying “all”, and I think I tracked the code to here where I see that or “everything” just sets a huge number.
Testing “all” and “everything” on two very corrupted (but same size) dblock files gave two “Hash mismatch” errors, so I think that refutes the stopped-early theory. We now can do “full” “wide” AND “deep” verification, provided “slow” is also permissible, and we both commented on how to start fresh while assessing damage.