Does Apple care that much about a GPU for the Air? I wonder what the split is for machines like the Mac Mini where you can get the GPU upgrade.
I don't discount the delivery volumes being a major factor, depending on why they could not ensure delivery. It's kind of interesting because if the AMD chip had benefits that Apple saw as a major advantage, they could have thrown them a ton of cash to improve production. We know Apple gets first grab of components by using that stockpile of cash to pre-pay for parts. The big manufacturers can buy a lot of chips, but how fast will they take delivery, and more importantly, be able to pay for them?
As a freelancer I have a few clients that pay me on the day I work, and one that has taken almost 90 days to pay (and many in between). You can guess which ones I give priority to when booking my schedule.