It is as simple: The CB provide you with a reason to wage war - and that is actually quite powerful. The huge discounts on AE allowed easy snowballing and abuse.
By nerfing the CBs expansion is slowed down a bit, making early game blobbing / domination a bit harder, providing you with a more challenging mid and late game (and harder choises for conquest / wars).
As for the changelog:
Its quite easy to "miss" some changes. They cab either be last-minute additions that didn't make it onto the list or got lost by human error. Happens to my mod changelist quite often. No evil intend needed.
(Although in this case they actually seem to be on the list.)