Its not really a scam but they lure people in with false promises/advertisement and then when they want just take it away.
Casinos change their rules and TOS from time to time but it's unethical if they did not announce it or did not make members aware of it, but it's good that you posted it here so people with similar situations will be fully aware of this, it's recommended to always check the casino's rules and TOS or be active in chat so you are updated on any change of rules especially to VIP.