Hi Tim,
Below the info from Microsoft but not clear
https://support.microsoft.com/en-us/help/10739/windows-10-cellular-settings#:~:text=Select%20it%20if%20you%20want,Let%20Windows%20manage%20this%20connection.
Per my own experience, I think “Let Windows manage this connection” means Windows can activate data session when WiFi/LAN is not available, thus it changes to “Connected” for data transfer thru 3G/LTE network.
However, when it is not connect, the modem still registered to the network, that means it can receive/transmit info with network (i.e. call/sms).
So the transmitter is not completely off, and it still can emit RF.
If you need it to be completely off, you may need to use the “airplane mode” option.
Hope it helps.
Thx