The MacBook Pro 2018 has requirements for repairs that affect the display, motherboard, touch ID, and upper case. This includes the keyboard, the battery, the trackpad and the speakers according to the document. For the iMac Pro, this requirement applies only to repairs to logic boards and flash memory.
Repairing any of these parts in an iMac Pro or 201
The Apple Diagnostics suite is limited to internal use by Apple stores and Apple Authorized Service Providers, which are part of the Apple Service Toolkit. As a result, independent repairers without Apple certification may not be able to repair certain parts of the iMac Pro and 2018 MacBook Pro.
Finally, if the iMac Pro and the 2018 MacBook Pro are classed as vintage products, meaning that they no longer receive any hardware service from Apple, alternative channel repairs may not be possible.
MacRumors has asked Apple for a comment.
This requirement results from the T2 chip, which integrates several previously separate components, including system management controller, image signal processor, audio controller, and SSD controller. It also has a secure enclave coprocessor for secure boot, encrypted storage and Touch ID authentication.
To initiate a Mac repair, visit the Get Support page at Apple.com.
Update: Despite the specific wording of the Apple document stating that the Apple diagnosis is not executed after replacing certain parts in Macs equipped with T2, the system will not be repaired IFixit experts replaced the display and logic board on a 2018 MacBook Pro, and it remained functional without passing a diagnosis.
iFixit is not an Apple Authorized Service Provider, so it seems that independent repairers should be able to fix the iMac Pro and 2018 MacBook Pro without any problems. It's unclear why Apple's document suggests otherwise.