You know something, what's the Url of the page you are checking for "IUP stock" in Safari (after being redirected from the Apple store app)? Thinking about this some, when going thru the app store to order through the IUP program, you are thrown to Safari to reserve an iPhone. I don't see why anyone couldn't use that same Url that is generated for you to check for "IUP stock". It doesn't seem to be tied to the iPhone or account that a user is trying to upgrade from in the Apple app store app.
*Ignore* Looks like the US site has a different setup lol
Ive been eagerly monitoring this thread, from the UK but wanted to throw my two cents in.
Notice the URL, where it says 'Channel='.... if you notice it takes you to Channel 1 if you are using desktop and Channel 2 if you are using Apple Store App
This is the UK web one - https://reserve.cdn-apple.com/GB/en_GB/reserve/iPhone/availability?channel=1&sourceID=31AC6A1A95EE1605-0E240B55C204205D&rv=0&path=&iPP=E&appleCare=Y
This is the UK Apple store app link - https://reserve.cdn-apple.com/GB/en_GB/reserve/iPhone/availability?channel=2&sourceID=31AC6A1A95EE1605-0E240B55C204205D&rv=0&path=&iPP=E&appleCare=Y
I have been trying to trick the system for a few days, hoping that there's a loop hole or a channel which will show restricted stock. Clearly Apple are filtering by device or browser info.
Apple have used the URL change in other areas of their website & design to...useful in finding out what mapping data they plan to use in the future