You're right is it something like misleading advertising? It has happened to me with several sites, especially in casinos, once I do not remember the name of a casino that I started playing crash and they give a faucet to start, with that amount I started to win and I did just what I needed to process the payment, When I went to make the payment, they told me that I had to deposit beforehand, that if I didn't deposit I couldn't withdraw, which I thought was a scam, so that's false advertising, and that's what you should be careful about.
But didn't they have those small print on the faucet indicating that money earned using the faucet could only be withdrawn after a deposit?
Either way, regardless of the offers that online casinos offer, it is normal for a person to first make a deposit and then be able to withdraw the money won. But this does not invalidate the gain, the person can deposit the minimum amount and then withdraw everything right away.