I do understand why they do it, they want to stop people with multiple and fake accounts.
However I agree with you that they should announce this at the start because I personally would never participate in a bounty campaign if I knew there was KYC.
But because they all say that the rules can change during the campaign there is nothing you can do about it.
I have participated in 2 campaigns on bitcointalk where I got nothing or stopped during the campaign because some stupid rules came forth in the middle of the campaign so now I'm trying to only participate on bounties outside bitcointalk.