Thanks, @David Gugick. That makes sense.

A related question: What about the new synthetic full backup? Is that appropriate with S3/Glacier?

What I see is this: My existing backup plans that save to Amazon Glacier vaults appear to still run, at least for backup. (I have not tried a restore since upgrading to CB 7.0).

But, if I try to edit one of these plans it will not let me continue past the second screen of the wizard. It gives me an error: "Amazon Glacier is not anymore supported as a backup destination."

It will be interesting to see if the new backup format, with Wasabi, can price out reasonably close to Glacier with the old CB backup format.