Thank you for following up with me on this. I did some additional digging to ensure that I fully understand the current flow available to merchants, and the changes you are asking for.
In the example you linked to, that is referring specifically to merchants who had the option to enable this functionality (Inventory and Fulfillment in MARKETS) as a beta when it first rolled out. If you did enable this feature when it was available then you can continue using it for now. It is not available to re-enable, or enable on stores that aren’t using it currently.
This means that the standard experience is that the storefront shows inventory based on availability across all warehouses, which could lead to customers being able to checkout with inventory not available to them at this time. Our team is aware of this limitation and how it can affect some merchants and their customer experience. We are continuing to work on this and improve the tooling we have available.
Ensuring that you have the correct shipping profiles setup though will help stop customers from being able to checkout with inventory not available to them at this time, which is where setting up shipping profiles comes into play.
If I am missing anything, or off the mark, please let me know! Shipping and fulfillment for international orders can be a tricky subject and I am happy to continue looking into this if I can.