We published an article about Bethog a while ago: https://www.btcgosu.com/blog/guides/casino/is-bethog-legit/ 
Guys, I don't know when you will see this but, read this article to know more about BetHog. Believe me when I say you 5 minutes spent reading it will e totally worth it. Keeping their promotional threads active and doing things underground gradually to make things good in the casino is not a bad idea. And before na casino use a private group in telegram, they know what they are doing. Every casino has their different groups in telegram. Some have general groups where everyone can join and participate and that group is different from the support group and moderators groups. There is a group for moderators and for the support team. So if BetHog has private group, they will still have another groups for different communications.
What is worth doing is worth doing well. Aside being an already established casino, it is up to the BetHog team to determine what they want at the stage and if having a private group is what they feel like would work for them to have good control and monitor things from the customers end closely, then that's great. This is to support your comment with same thing I said the previous day.