Yes if the REMOTE
connection on your radio sees the DTR (handshake line on the connected PC COM port) active the radio will see this as a command to turn on, although the power is derived normally.
Unintentional reasons for this could be a program running at startup that accesses the COM port in question or a sequential COM port interrogation program.
I use Airmail radio email
program with PTC-IIex TNC and radio control to ICOM
M802 using second dedicated COM port. This allows me to turn on radio via Airmail which in turn powers TNC. Freqency selection is then performed automatically from Airmail propagation module or terminal window, & I can also use Tune button on latter. When the terminal window closes radio is turned off.
Thinking about your setup again it appears you may be connecting to the REMOTE
dsub connector on M802 in error, as this is designed for radio control. You need to use one of the two possible audio in/out connectors (ACC or AF/MOD) to receive audio for radio fax decode.