By unlocked parts, they may be referring to how Apple serializes parts in iPhones so that you are forced to pay for repair at the Apple store. Part serialization means that if you took two real iPhones apart, swapped every component with each other, and tried to use the phone, certain features just stop working... Here is a demo from Hugh Jeffreys, who has demonstrated this problem with many recent iPhone models: https://youtu.be/dbRKQ0OjQeE
I just hope android devices never adopt this anti-feature like has happened many times in the past with Apple's anti consumer design choices.
What you said + nicer motherboards often come with bios flashback which should (IMO) be a mandatory feature for motherboards on platforms like AM4. Makes CPU compatibility much better since a supported bios version can be flashed anytime, no matter what CPU is currently installed (if a CPU is installed at all!).