Why do both the iOS/Android phone and the Redmi Buds 6 play sound simultaneously when receiving a call?

On iOS, the phone automatically selects whether the ringtone plays on the device itself or through connected accessories based on the silent mode status.
If silent mode is off on the iPhone, both the phone speaker and the earbuds will play the ringtone simultaneously, as this is the default behavior for ensuring the call alert is audible.
If silent mode is on, only the earbuds will play the ringtone, as the iPhone mutes its speaker. This design prioritizes privacy by ensuring only you hear the ringtone.
On Android, similar behavior could occur, however, it depends on specific phone settings and configurations.