I guarantee it's a third option: When Apple has a bizarre, unexplainable limitation, it's because of a highly opinionated hyper-pure UX design decision. Having

I guarantee it's a third option: When Apple has a bizarre, unexplainable limitation, it's because of a highly opinionated hyper-pure UX design decision. Having multiple timers running is inelegant and sometimes confusing. So instead of giving users any agency in that situation, they just ban the very concept as a whole. If they feel enough pressure, and they can come up with a satisfactorily simple UX, they will usually eventually fix the hole.