I'm pretty sure that there are some bounties that did something like that, bounties that do not use an independent escrow that is not part of the project can always pull something like this, they can always change the rules in a way that benefits them and that they know a great deal of bounty hunters are not going to accept and save themselves a great deal of coins, and then when the bounty hunters point their fingers at them and accused them of cheating they can always say that they just refused to follow the new rules and that they would have been paid if that was the case.
that's why Escrow is so important. everything regarding that rules should be stated from the start of the contract. an example of the laziest thing is when we have to verify KYC. if not then no get reward. so maybe if escrow is implemented it can be easier to solve that problem
While I agree wholeheartedly that the rules should be stated from the very start especially the important ones like whether or not participants will have to go through KYC most bounty campaigns do not do this and change the rules during the middle of the campaign and the worst part is that the participants cannot complain because if they do that they get kicked out of the campaign and also because many bounty managers put rules from the beginning that allows them to change the rules so bounty hunters have basically no protection if they decide to join a bounty without an escrow.