These messages issue the commands, that will either allow for media eject and/or eject the virtual CD-ROM, … in order to switch the device into 3G modem mode.
The /etc/usb-mode.json configuration file looks partially like below. The usb-modeswitch package includes usbmode tool with json-based configuration instead of classic usb_modeswitch binary, and a Procd service running to switch automatically all modems as soon as they are plugged in. USB dongles also may or may not need to be switched to high-speed USB modem protocols to use their full potential. It's common for 3G/LTE dongles (and some smartphones) to show up as a virtual CD drive offering drivers and utilities to use them on Windows/Mac, then after you have dismissed this somehow then it will switch to the “useful” mode.
