I believe they theoretically could, but I guess they don't consider it cost-effective, or are waiting to see what happens, or they are already planning to do it

I believe they theoretically could, but I guess they don't consider it cost-effective, or are waiting to see what happens, or they are already planning to do it but it will take much more time. Regarding your "shipping to Australia" example - that is just regular fulfillment of Amazon.com orders from US stock, with an international destination address. That will continue to work in all EU/UK marketplaces, this change is only about fulfilling e.g. amazon.de orders from UK stock and vice-versa (EFN) and cross-border movement of not-yet-sold stock (Pan-European FBA). Regarding EFN: There is already a similar cross-border program called Amazon Global Store, where Amazon ships e.g. US stock to amazon.co.uk buyers (example: https://www.amazon.co.uk/dp/B00AFTQ4X8 https://www.amazon.co.uk/dp/B00AFTQ4X8). It also works for 3rd-party sellers, in which case Amazon buys the item for itself in US and then ships it to the customer in UK ("Allow Amazon to buy my products to sell globally" in Amazon US seller settings). However, this is much more limited in scope of products compared to what EFN currently is, and those items do not currently ship "internationally" (e.g. I can't order a Global Store item from amazon.co.uk to Finland like I can with EFN items). Regarding Pan-European FBA: I believe Amazon does not want to move non-sold 3rd-party stock across customs jurisdictions, or at least it has never done that before. Shipping sold items to end-customers (which they do, e.g. Australia example above) is a bit easier, as e.g. valuing the items is easy (it is exactly the amount the customer paid), and Amazon never has to be at the receiving end.