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I agree that 30x requirement is not something normal but since the casino is offering free deposit to its customers, they want to make sure that no one is able to withdraw that amount

Anyways i consider it a good initiative as it will allow people to make an account on this site and try the games and interface of the casino, even though they have to wager 30x and survive their balance in order to make a withdrawal.
Also the most important part is that people will give honest feedback after playing with free money and those feedback can be an asset for the OK.Fun to grow.
It is something normal and standard rule when it comes to free spins or no deposit bonus given on registration.
Some other casinos may use 40x wagering requirement so 30x should be lower than the most used wagering requirement.
As you said yourself, this kind of bonuses is given to let player explore the casino by playing some available games, not to make money.
Lets say some players able to complete the wagering requirement and withdraw some money, it is their lucky moment while trying the casino using the free bonus balance.
Anyway, they should create separate thread for this offer because it is not allowed to offer free bonus in this gambling board, they should create a new thread in the games and rounds board.