It's true, it's not fair for those who work for weeks. But these rules will still apply so that all participants can better support the project to completion. In my opinion, there are a number of campaign managers who give participants to their signature campaigns the opportunity to remove their signatures but must be reported in advance. Without reporting, all bets will also be deleted. I think this is fair enough for participants.
why you said it's not fair? as you can see usually that rules already there before you join it
so it will be good if you not join it at first and just choose another bounty
yes agree with you, when you think its not fair you havenot to join and choose another bounty . all requirement of signature campaigns is like that so you have to follow the rule and waiting for end of campaign to get reward
its look hard but requirement have to do, if not you have unfair in your life