This is probably one of the oldest scams in the book and it is still working because people are dumb. Some random guy contacts you on TG or other social media platforms, saying that he works for the casino site or found a vulnerability and will make you a millionaire if you agree to share the spoils with him. Of course you have to deposit first. Same old bullshit story. You deposit your Bitcoins, and then you get nothing in return. This is a very common scam, especially on TG. Do not fall for it!
They targeted new gamblers who are not aware of this scheme, this is indeed very old I remember asking about this here in Bitcointalk some three or four years ago, it's really this old, I just knew that scheme will be back because it works for users who are not aware on how these things work and if the potential victim is greedy he will likely fall to this scheme.
Schemes to scam people are always recycled if they made money in the past, they will always have victims in the future that are not aware of this, so it's better to share this scheme with friends who are new to online casinos.