The bit about the iPhone 8 doesn't make much sense to me, apart from the storage, the rest of the iPhone 8 is the same, whether it is a (Red), 64GB, 128GB or 256GB. If the screen breaks on an 8, it is the screen that needs replacing and that is the same screen as a "vintage" 64GB or 256GB or a supported 128GB model...
I could understand saying that, "the 256GB motherboard is no longer supported, we will have to downgrade it to 128GB, if you want to repair it." But, "sorry, your iPhone 8 is the wrong model for a new screen, but the guy standing next to you with the same phone, with a different memory configuration can get his screen replaced," is disingenuous.