My take is that Apple is ‘doing the right thing’ here. Clarity, humility, and rather fair pricing on new genuine Apple batteries, installed and with an Apple battery warranty. This may cut into aftermarket replacement battery sales.

Aftermarket batteries may be of lesser quality and creating their own issues for Apple’s reputation, especially if they impair ongoing iPhone reliability more than a genuine Apple battery.

While the current policy statement says the battery replacement discount runs until end of 2018, Apple may well create an ongoing ‘discounted’ battery replacement program. It would engender goodwill and ensure the average ‘older’ iPhone continues to perform well and reinforce the brand.

Very recent models of iPhone (8, X) have had significant increments in stated run time over iPhone 6 or even 7. Apple may be increasing baseline battery stamina in part to further delay onset of performance reductions driven by battery aging.