Allow changing the archive passphrase? gets into some relevant issues.
You don’t HAVE to restore everything, but a simple small check would help ensure things work…
Minimal footprint restore test has some relevant comments, including some on hash checking.
Hashes for each source file are actually in the DB already, and used to verify a restore is good.
Restore for test won’t do that, but merge might. That’s why I asked earlier about intended result.