I'm not going to claim lag doesn't exist in iOS. I will claim my device barely lags, at least not much that I notice. I will also claim it doesn't lag everywhere. I'm not going to back up a claim I don't believe. Lag exists.
I already stated no software is perfect including iOS so as to not state an absolute which is proven false with one exception. My assertion is that iOS 9 is not a laggy, stuttery pile of garbage as has been suggested.