It might seem cynical, but it appears to me to be a marketing ploy/PR stunt to show that the BH8 release was well received/popular.
It has the “carrot” of Town Hall related rewards to tempt those who hate BhB to reluctantly take part in order to avoid missing out on a book or some resources to help their advance in the original game.
I think our clans (lack of) BhB activity and the reasons for not enjoying the BhB gameplay are similar to many who have posted on here, so I will not expand on that.
Our 49 member clan has 2 players who regularly do their 3 wins per day, (only 3 accounts have ever pushed above the 3k points) some do occasional attacks, and many of us just use the BhB as a Gem resource, I know we were similar in activity to Onyx DS’s research about 5 or 6 months ago on BhB activity.
I have polled my clan to see what they want to do, are we partaking in these games as all? The rewards (apart from the book of heroes) we can get in main village with very little effort during normal raids.
If we get active as a clan and try to get to tier 5 to gain the book of heroes (as tiers 1 to 4 are not worth the effort), our clan stats for attacks and potentially 3 plus wins per day are going to take our activity from <=5% activity to =>75% activity, showing the “success story” of the BH8 release.
This activity surge would have been much less, as others have said, if the rewards were solely for BhB. The activity figures for ourselves and the overall clash population might have risen even if the rewards were for BhB only as those interested had the double rewards of the additional Battle Fest 8 hour reset, plus the BhB ones.
Anyway, the regular surge of players logging in to take tasks at the beginning of CG has not happened, just disgruntled players logging in to see the task board so far. 12 players actively looked at board, one task of clearing obstacles completed, all others not selected tasks.

