The data on the device is encrypted. This allows you to install a different OS on the device, but it won’t be able to decrypt the users data without pin code.

The data on the device is encrypted. This allows you to install a different OS on the device, but it won’t be able to decrypt the users data without pin code. You could potentially flash a new firmware which contains a keylogger and sends the pin to someone. Or that waits for the user to enter it (decrypting the disk,) and then siphons off the data. But on your own with a stolen phone and this you won’t be able to read the data.