In the first place, they didn't mention anything about kyc things on their campaign's terms. Whether its necessary or not for hunters to perform kyc in order to join the campaign, I think it wasn't totally surprised if they would charge hunters to do so once the campaign ended.
Yep, changing rules and introducing KYC is standard practice of majority of bounty campaigns as their goal is to send as less tokens as possible, and KYC is one of the best ways to eliminate bounty hunters, all under pretension of wanting to eliminate the scammers.
Reducing the pools are not really a problem if its drop are reasonable and communicated with participant before distribution (Example 10% of Signature goes to Twitter because of .... ), but this one is locking Bounty group and reducing 99% of its pool which cant be accepted at all.