It only says the Warranty is invalid, not that they "can brick your phone"
Moreover, notice that they carefully follow the law's requirements by NOT saying that just using third party parts voids the warranty. Because by law, they cannot.
Instead, they say that it happens if a part causes DAMAGE, because the law does allow that.
I agree that it's not about making money. It's probably more about lazy coding. Someone should've thought it through more. Perhaps warned the user, and then allowed them to re-validate by entering their passcode. At the most, disable TouchID and force use of the passcode. Disabling the entire device is just wrong.
Could be. The basic idea is good, but the current implementation sucks. Whatcha bet that it'll change in future releases?