Ofcourse it is!
Nowadays, I notice most of bounties have strick rules, making bounties more organize and I like that Bounty Manager requesting Proof of Authentication to limit scammer .
It's been one of major mistakes of bounty hunter like me not to read rules and requirements of each bounties ending up not getting stakes so it's very important to read and understand each rules to ensure that we're doing the right thing and not wasting our time and effort.
in fact almost every bounty campaign has almost the same rules. but there are many who are misused, especially in social media campaigns. there are many who use signatures but don't make any posts. I think the manager must kick someone like that, if you need to get banned