What makes it worth doing isn’t about the results, IMO, but about maintaining a secure election. A risk review - especially by hand - will not only provide an audit that verifies if an issue exists, but will also allow action to be taken to prevent issues in the future should there be any shenanigans.

So if all the ballots were fake, yes, it would be really important to know how. That’s several orders of magnitude larger than any voter fraud I’m aware of.