Apple’s claim that they must disable an iPhone after its home button is replaced for security reasons makes no sense. It’s Apple’s attempt to get even more money out of its users.
If Apple’s software can recognize the home button has been replaced, simply disable the fingerprint sensor and require a passcode. Inconvenient for a user, but not a catastrophe.
People can still have the pictures of their kids, pets, texts with loved ones, and all the other valuable content we keep on our phones. It doesn’t all just disappear because they chose the fiscally responsible action of having their broken iPhone fixed by someone other than Apple.
The most likely reason for Apple doing this is profit, not security.