I find this very hard to believe, mainly because these kinds of things are incredibly, meticulously planned out and the amount of mistakes that would need to happen it just doesn't make any sense.
You don't just have a situation where different projects are passed between separate production lines or anything like that.
The most likely situation right now is that NX is using Zen and Polaris in one of the first APUs available, so they have to wait for sufficient quantities to be shipped to Foxconn, then final manufacturing there also takes time.
The updated XBox is rumored to have gone into production in like Feb, it would be basically impossible for this kind of rumored mess up to happen.
Assuming this is AMD making an SOC for NX they've had the design win for ages, no doubt Nintendo would have been in constant communication about where the project is at and checking on their investment, AMD can't afford to make this kind of mistake.
Either NX is using a Zen/Polaris based APU/SOC or NX launch games needed more time in development.
