It happens from time to time... Except for this case with BC.Game, which happened on December 30, a few months ago, something similar happened to me with Rocketpot. Or it was more than a few months ago, I couldn't find the mail. Messages in the trash are being deleted after 30 days... I don't even remember the others, I have been gambling in crypto casinos since 2015, and I was active in many casinos and crypto services.
And another thing is that they (the hackers) only have his email address they still don’t have the password or login details of the email so it’s impossible for them to have known if his account or his friend’s account have been funded or not, they are simply just trying their luck.
I agree with you, these hacking attempts have nothing to do with the current balance. I received similar messages from casinos/services where I have not been active for a long time and where my balance is zero.