“Although we enthusiastically awarded it a solid score at launch last year, thanks to its innovative repair-friendly architecture—of which we remain big fans—the reality for folks trying to fix these things has been very different. Most major repairs on modern iPhones require Apple approval. You have to buy parts through their system, then have the repair validated via a chat system. Otherwise, you’ll run into limited or missing functionality, with a side of annoying warnings. ”
Source : We Are Retroactively Dropping the iPhone’s Repairability Score | iFixit News