It's an elaborate workaround for Backblaze's pricing. What I was alluding to in my comment was that they charge $8/computer for backup, but without any limit to the amount of data they'll sync. They won't let you sync network drives, but they will let you sync external USB drives, so syncing a network drive to an external drive allows you to basically sync that external data to a cloud backup.

That way I have 3-2-1: 3 copies, on at least 2 devices, on at least 1 remote location. For $8/month (but also, some up-front investment in physical stuff I had to buy).