It's a footnote because it's the most inconsequential part of the ruling. The copyright infringement status of making thousands of unlicensed digital copies is not affected by whether you own a physical copy or not.
This ruling isn't about making thousands of digital copies. They're no longer able to offer even 1 digital copy.
The CDL is where they would buy N physical copies of a book, and then allow N active rentals of the digitally scanned version of that book with a waiting list for when people "return" them. Can't do that anymore.
The bytes were copied thousands of times. That means they made thousands of copies. It doesn't matter if the UX describes a concept of 'a digital copy' which requires that a new copy not be made until the old copy is deleted; copyright law does not say that this exempts you from the usual rule against making unlicensed copies. What you are thinking of, where you own 'a digital copy' of a book, is owning a license (as you have checked an 'I understand' box about a dozen times), not owning a copy. IA does not have permission to sublicense copies it legally owns (and didn't legally own the digital copies to start with, as their purposes weren't within the ยง108 carveout).