Most of the Telcos book and pay in advance to Apple for iphones. If stock is easily available means the telcos over estimated demand now it could be that sales are not as high as previously or Telco overbooked. Talking to people around me that use iPhones though most feel 8 is not worth upgrading and X is too expensive so many of them have gone for 7.
Wouldn't that be a clear sign they aren't selling as well as expected?
It could also signal a shift in strategy by Apple to overproduce, or better models that more accurately estimate demand.
It COULD also be a sign for the end of times.
The suppliers received reduced quantity orders, so I doubt that.