I just want you to ensure you're not confusing B2 with the product being mentioned here. This is a custom Backblaze product which only works via their apps and I don't believe is available as a storage backend for backups through something like rclone.

I never tried this particular Backblaze product because I don't trust a opaque blob touching my most valuable data nor do I trust unlimited plans that dont mention what the limits are, atleast in fine print.