If you see such phrase being put in place, you should stop and think about it for a second. Don't just jump in and participate without thinking it through. If you decide to join, then that was your choice.
Remember that nobody in this forum is forced to participate in any bounty campaign and, the problem is, most people always have high hopes about the campaigns they have participated; but, when things go sideways and doesn't meet their expectations, you'll hear them complain about it over and over again. You can't really blame a startup's bounty campaign for having such rule. Crypto-market and as well as IEO/ICO's are unpredictable, which is why a startup aiming to get funded through cryptocurrencies have to be flexible in order to succeed. Such abrupt changes may happen even before the bounty campaign has ended.