1 - Wi-Fi client devices would like to see a 'clear winner' in their decision matrix when choosing which access point to associate to.
2 - For each and every single 802.11 frame being transmitted, it must WAIT for an opportunity to Transmit - following a logical process to see if the channel is clear, and using randomized time slots to try to NOT transmit while other may be transmitting.
3 - So when you have too much CCC - meaning more than one access point on the same channel above a trigger threshold, then that transmitter will back off and WAIT. Thus keeping devices from transmitting data when and how they want.
4 - It is NOT about 'green is good' - showing a cumulative group of data that only shows the highest RSSI on a map. Much more important is the visualization that shows where the system already has too much CCC baked into the design.
5 - Turning down the Tx power 'barely' moves the CCC needle. Placing access points properly, using wall attenuation characteristics properly, using the right antennas - all do a much better job of minimizing CCC than merely adjusting Tx power.