I seem to remember that on Airbus FBW: by using the select function to tune the offside VHF; the previously active frequency of that box is lost, so going back to the previous frequency is not possible, (unless you write down every freq.).
Arguably there is less chance for cocking it up and temporarily losing comms if each RMP panel is just used for its onside radio - RMP 1 for VHF 1, RMP 2 for VHF 2 - as if the RMP was the actual radio. The association of the physical location of the RMP with the radio function is powerful and helps avoid changing or transmitting on the wrong radio.