I'm pretty sure there was no direct malice here (except for the usual Apple disregard for 3rd party components), but the security reasoning behind this move is

I'm pretty sure there was no direct malice here (except for the usual Apple disregard for 3rd party components), but the security reasoning behind this move is still questionable. The only danger of a compromised Touch ID sensor, is that it could record your fingerprint and let the attackers replay that fingerprint to access all your encryption keys on Secret Enclave. That would be a huge vulnerability, if there hadn't been thousands of other ways to record your fingerprint, and while most of them are less accurate than a trojan Touch ID, they're also much easier to pull off. And at the very worst, if a sophisticated malicious actor got the chance to meddle with your phone, they could just skip the Touch ID sensor altogether and install a stealthy fingerprint digitizer in the touch screen or on the back of the phone. So in short, Apple's security measure, if my understanding is correct, does absolutely nothing to protect the user.