Where's the evidence they're coming from Android?
I got the impression from reading (perhaps too far?) between the lines is that this generation of iPhones has had a larger proportion of converts from Android. In isolation this might not be very useful knowledge.
However – and this is pure speculation – it's also conceivable that a measurable number of people who wanted a large screen smartphone gave up waiting for Apple and went with one running Android by default, because it was the only option.