I'd ask you to please enlighten us where all the iPhone users are that get their back glasses replaced due to the coating wearing off, which simply isn't something anyone does (contrary to battery replacements), but we're in a thread about a MBP and if you claim the MBP housing is a consumable due to some coating that iPhones have, you are clearly not arguing in good faith.
You asked me why Apple singled out battery and chassis as items for replacement in refurb products. Apple only guarantees battery and chassis replacements on refurb iPhone. Apple does
not guarantee such replacements on refurb MacBook. They replace those items
if needed on MacBook. This part has been settled.
On iPhone, the chassis is considered a consumable item for obvious reasons. People put iPhone in their pockets. Unlike MacBook, it does not have feet on the bottom chassis. The PVD coating on iPhone can and will scratch. The oleophobic coating on the rear glass can and will degrade. Just because a recoating service is not sought by many iPhone customers, has no relation to whether Apple considers it a consumable.
It cost 3 times more than the most expensive computer I had ever bought before. It sounds like my problem was somewhat different than yours though. You can read about mine here: