Thanks for the detail BDiONU
RF congestion has been addressed to some extent by the introduction of 8.33 frequency spacing.
Just as a point of clarification, the supposed benefit is relief of congestion of the radio spectrum around 1090 MHz where the transponders work, not of the aeronautical comms RT frequencies. I thought exactly as you did when I read the "RF congestion" section title in the CBA, but what they're getting at is basically that the selective nature of Mode S means that there's less going on at that frequency.