I did a battery replacement on iPhone 6s around ten months ago on iOS 12 something with third party battery and the battery health feature was disabled. HOWEVER, I factory reset my iPhone and the battery health feature restored. Simple as that. I don’t know whether it will work with the latest iPhones on latest iOS but you should try it out.
They are not interchangeable: iPhone 6 Battery Compatibility All iPhone 6 (Not iPhone 6 Plus, 6s, or 6s Plus) iPhone 6 Battery iPhone 6S Battery Compatibility All iPhone 6s (Not iPhone 6, 6 Plus, or 6s Plus) iPhone 6s Battery - iPhone 6.

For the record, the difference between the iPhone 6S and 6 batteries is only about 5% and the difference between the iPhone 7 and iPhone 6S is only about 12%. Those are theoretical differences. Batteries are like cakes, you follow the recipe but always get a slightly different result. Just because it says 1715mAh doesn't mean it is.

2 days ago · The iPhones included in the settlement were the iPhone 6, 6 Plus, 6S, 6S Plus and SE running iOS 12.2.1 or later, as well as the iPhone 7 and 7 Plus if they were running iOS 11.2 or later before

The iPhone 6 has a 4.7-inch display with a "2x" resolution of 1334 x 740 (326 ppi) while the iPhone 6 Plus has a 5.5-inch "3x" resolution of 1920 x 1080 (401 ppi). Both phones are said to offer

. 293 246 66 134 449 44 472 210

do iphone 6 and 6s have the same battery