iPod Touch 4, iPhone 4S and iPad Air 2 are rather dated instruments which I still use. From their cameras it can be said:
Lens covers are all anti-reflective coated,
Sensors technology has much lower performance i.e. less sensitive, already back illuminated ? Smaller aperture,
Slow electronics.
Then considering such defavorable conditions, why anti-reflective coating was retained for these instruments whilst further to your quote it may have been preferable to ommit it ?
The iPhone 11 series cameras in turn have:
Un-coated lens covers,
Back illuminated & larger sensor,
Much larger aperture,
Faster electronics.
I very much doubt _ but fairly enough I dont remember the scientific facts _ that under such favorable conditions that an appropriate anti-reflective coating on both faces of the lenses covers would so severely affect incident light rays transmission. For the answer, I shall consult a friend who is a laser researcher. We may even be able to perform experiments.