If they were to make the copy available for everyone through their own syndicator then sure, but they don't. The "copy" is only available for the original reader, who had legitimate access to the original anyway.

Under copyright, you're allowed to make full copies of works which you have legitimate access to, as long as you don't distribute them to others.

https://copyright.unimelb.edu.au/shared/using-copyright-mate...

To me, what Pocket is offering is like a warehouse where you can take books which you already own, and they're charging you for the warehouse space.

Doesn't sound like anything to do with copyright to me.