This happened due to constraints on replacement units for the discontinued GSM iPhone 4 16GB white. Those who faced hardware problems were given free updated to the iPhone 4S.
This was until early this week, the fruit company caught up with the demand for the constrained white iPhone 4 16GB replacement units. Now after catching up with that SKU, Apple now faces constraints of the black 32GB iPhone 4 and black 16GB iPhone 4. The CDMA/GSM unit breakdown is still not known.
Just like what happened in the constraint situation of mid-April when 16GB white iPhone 4 was short, the Genius Bars without the stock of the 16 and 32 GB black iPhone 4 replacement units have been asked to provide customers with comparable iPhone 4S units.
Even though these constraints are not faced by all Apple Stores, there are many who are facing a shortage, and these should clear up within a few weeks if the white iPhone 4 16 GB constraint process.
If you have a black iPhone 4 that needs to be services, now will be a good time to visit the Genius Bar! There’s a high probability you drive back with Siri.