The charging case of the Bluetooth headset has a built-in charging circuit and battery, which can charge the headset. Before being placed in the box, the headset connects to devices such as a phone via a Bluetooth connection. But in the box, after the earphone contacts the charging interface, the charger will use the bridge to charge the charging current through the earphone.
During this process, the headset is still connected to the Bluetooth device, but it will be in a low power state, using the least amount of power to maintain the connection until it is charged and then disconnected. Therefore, the headset placed in the box can be charged at the same time, and will not affect the connection with the Bluetooth device.
The reason why the Bluetooth headset has not been released, it is certainly the reason why you have not turned it off.