Not sure I am following this. Did Google release this because PG backups are not 100% reliable or the data corruption can occur due to hardware failure.
From what I understand with this Google tool, it has nothing to do with backups. It just allows you to check data blocks in a PostgreSQL cluster. Google advice is to run it before taking a backup, but that's about it.
This appears to basically be the same tool that's already included in PostgreSQL 11, and has been around in a few different incarnations (but unpolished) for years.
FWIW, in relation to backups, tools like pgbackrest already did this transparently during backup, and again PostgreSQL 11 will do it built-in.
It's quite possible Google was running this internally before of course, and a separate tool from others, but it's not exactly news... But they do outline a very definite problem, which is that if you get physical corruption in your database, it gets included in the backups. And if it's in a portion of the database you don't use a lot, checksum failures won't be noticed until you actually try, which is way too late.