You have that on all platforms, Kryptonia does offer you to option of rejecting a payout if a task is not correctly completed.
If a Task requires you to sign up via a link, whether you accept the task it is you decision. Likewise don't do the task with no intent of doing the sign-up, you may be revoked which is not good for your standing in the community.
Task is there with a specific call out to assist the person who put the Task up, paying members to complete the task to do so if they so wish.