Great. Let's not slow down CPUs coupled with aging batteries and instead have a full system crash suddenly at the most demanding moment. Sure that would be much better.
Most phone PCB designs do not account properly for the scenario "battery gone bad leads to undervolting of components" at all, the best you're gonna get is the BMC cutting off everything when the voltage at the battery drops way too much - but that is a failsafe mechanism, the flash, memory and processor chips will have undergone brownout events before the BMC emergency shutdown hits.
We were talking about Apple here. If they don't know that a battery can get discharged, maybe they shall do something else. For a SWE might be ok. For a HWE no.
I wonder why... /s