The 1st iphone went out on June 29, 2007 and after 6 years they keep making mistakes knowing the huge worldwide demand of iphones.
I am pretty sure that the Marketing department has a very good reason that explain why they keep having these issue after 7 years of iphones.
Instead of launching the new iphone on the 20th of Semptember they could wait the 20th of October to have millions of iphones "ready to be shipped" instead "ready to be built" letting millions of people waiting for something that will arrive "some random day at some random time in October".
I am sure that many of you will reply something like "oh this is all strategy to generate a big hype so people desire even more every iphone they make". To me is just "oh their Marketing department is so dumb that they are not even able to avoid those basic mistakes after 7 years".
Anyway, at the end of the day, Apple will always win and people will be ready to wait for months/years to have the next-new-amazing-super-gorgeous-blablabla... iphone.
Well done Apple.