So, can the button used be changed or does it have to be standardized across devices and which is why it's the volume down button? Because the squeeze function

So, can the button used be changed or does it have to be standardized across devices and which is why it's the volume down button? Because the squeeze function on Pixels or assistant buttons on other devices could be used instead, though that's just me wondering out loud for an alternative user-facing implementation because the use of volume button seems strange to me.