I think anyone that have been here before with their active email will get this for sure. So if you are not getting it, means that you are not yet played it here. And may be you are still active according to their terms. We never know how they support team manage to get it done but yes, most of the inactive account will get this 50k satoshi. I also got the email but unfortunately I can't use it
I got the same welcome bonus 2-3 years ago but it's not through their email and it was an pm from one of the admins. Maybe we're in their list of top users that wagered and reached a certain amount because back then I used to play almost every day and remember having like 2-5btc on my overall wagers before I went inactive.