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.
Some casinos have private and separate groups only for VIP and special players. those who reach a certain level of wagering get invited to these groups ,where they have different bonuses and cash rewards from time to time, and since those rewards are only for VIPs to claim, no outsiders are added in those groups. I have seen on YouTube where streamers are allowed to open their chats only to subscribers and also to members who have bought their membership and pay a specific fee every month.
I know this isn't relevant, but maybe BetHog has decided to only keep the group to users who have accounts with them, and as you said, they might decide to create another group for general discussions and that might be open for everyone.
The team knows what they are doing, for sure.
Your idea is good it can be considered as another level of security for only vip top wagering bettor to gain access to but I must bring to your notice that scammers these day spend enough money to make their phishing activities look legit. It'll be difficult for a scammer in form of a regular gambler to convince others into falling for his scam but when the gambler is accepted into the VIP group or even presented with a vip badge, it'll be very easy to convince others. And that is why I still stand for the idea of monitoring the system by a smart tech guru and the AI detector.