Earlier quoted context omitted.
Seems more like short sightedness than "petty revenge." The new home button hardware can't be securely validated, and a future OS update fails on the unexpected condition of invalid Touch ID hardware. I can imagine that this wasn't a prioritised testing scenario, likely not even considered by Apple when developing iOS. It's a lousy way to fail — the phone should just disable Touch ID and Apple Pay, and anything that…
The scenario they're protecting against appears (to me) to be a bad actor changing the hardware. If the Touch ID sensor is bad, and you propose falling back to a PIN, who's to say the digitizer isn't compromised too and is recording touches? Sounds a bit like a downgrade attack if they didn't fail fast and hard at the earliest opportunity.
This botched handling of replaced hardware that hasn't been paired with the Secure Enclave ties into the above. Apple doesn't expect people to replace such hardware through a third-party, so they don't think to engineer their software to fail gracefully when it happens.