I have the 2 on the belly also, CI-122's. IIRC, you have the Icom A 210? I have a Garmin SL30, and an Icom a 210. When I was wiring my radio's in the basement, sometimes when I would transmit on the sl30, the Icom "rx" light would come on. I remember seeing the interlock function and trying it, and I saw no difference. That was a couple years ago.
I'm flying now, and the good news is both radios are working very well. I will remember to pay attention to the "rx" light on the Icom when I transmit, and see if it still does it.