It's probably because they wanna keep a soft-cap from attrition. Through some exploitation, ahum "strategy" with SC attrition was (almost entirely) bypassed. Effectively removing the cap for some. I think they wanna address this. While also continue to sell the "solution" for the "problem" attrition poses.
Attrition poses a soft-cap for everyone. With %
sold during events with event buildings, this soft-cap can be raised at a personal level and motivates players to continuously invest. To squeezing out that little bit higher attrition level for those few extra fights. Same goes with the GbG buildings. All designed to gain an advantage over competitors. It seems the rewards and ranking are an attempt to make guilds compete with each other and giving them goals resulting into conflict. At least it seems to be the intention.
In short, it's quite simple. The changes are aimed to discourage farming, making attrition relevant again, making event buildings sold valuable for players, to be able to maintain profitability. While also trying to motivate guilds to fight each other for ranking and special buildings.