Please note that its actually incorrect to say money is getting in or out certain physical place. If it becomes bitcoin, it is bitcoin everywhere. Bitcoin is border-less, once you change your country's fiat into Bitcoin, you have gained a worldwide asset. So rather than saying the money leaves Iran, you could say the money enters Bitcoin. It can still be used inside Iran at any moment, unlike doing the same with forex or some foreign bank account. The difference is huge if you stop to think about it...
It's not incorrect, especially if all people are doing is just converting their cash to bitcoin just so they can bypass restrictions so they can easily send it somewhere then cash out back to whatever fiat currency they want then all bitcoin has played a part in is transferring wealth. Not necessarily a bad thing as people are still transacting with bitcoin which is good, but if the money only technically stays in bitcoin temporarily then people aren't using is as a store of value/wealth, which still would be risky for them given bitcoin's volatility.