I have also received one. The format of the email is the same, but it asks me to check the fishing frenzy tournament. I've got the code as well but I'm not expecting that it will be a $10. I've taken one code before and claimed it, but I only got a few cents, am I complaining? no. But bc.game seems to be not trying to miss any active user they have before so, they want us to come back and stay.
The bonus terms stated up to 10$ bonus meaning 10$ is the maximum bonus you can received when you claim this promotion. Probably the amount is related to your VIP level or maybe a complete random basis.
I do get a lot of this bonus in the past but in BCD and fixed amount around 5$ IIRC.
This bonuses is good since it doesn’t have wagering requirements while you can YOLO bet it no string attached on high risk games. 
I agree, they're completely risk free and there is not a lot of requirements to get them. Just input the code that's emailed to us and those probably are unique code per user and the amount will just either shock or surprise you after wards. But then, it's free to bet it anyway and I've mostly spent it with plinkos. 