So go live without testing the backup in the beta at all?

Yes! Why build a backup process before you know you have data worth backing up.

The data recovery process needs to be validated too, preferably before customer data actually needs to be recovered.

Why go live if you don't have a reasonable expectation of users?

Worrying about HA when you don't have customers that need it is one thing, but I wouldn't want to be in a place where I have to put a banner on the website asking users to please make a new account because we had an oopsie.

To be fair, there's a big difference between "we do periodic backups" and "we can restore to any millisecond since product launch.

Sure, but it seemed to be that any backups at all were being called too frivolous.