Even everything above is followed correctly, still there's no guarantee that project will be good. However, if someone does enough research it's possible to avoid scam project. I am really bored on bounty and given up participating too.
There is absolutely nothing that can guarantee what the outcome of any bounty could be, even when the tasks are limited, with stakes counted promptly, it's still isn't enough of an indication that the bounty would end, but when bounties by certain managers, you can be rest assured that there is a better possibility of it being successful (or at least) pay it's participants.
You made a point here, personally I had previously joined a bounty campaign devoid of any of the flaws or flags mentioned by the OP which ended up as scam.
Bidium was the bounty campaign it was well organized and weekly spreadsheet update was promptly and responses to enquiries on telegram too was prompt and quick however at the end of the campaign none of the hunters was paid thus it is not never a guarantee to get payment maybe the manager handling the job might be considered.