Yeah I have also not heard about it on any other casino and think they are first one to implement the clan features into gambling aspects which is cool and you can communicate within your clan to build up you plans and then bet upon to see if you are able to win something and share the amount in pool.This is what we have seen in some games but not in gambling if I am right so great addition by team.
They are definitely the first place to do it, I have been gambling for over 8 years now and I can say that I have never seen a clan feature in any casino before, if there is one then it means that it must be a small enough place to go by without me realizing. I have gambled in all places that has more than 100 pages in bitcointalk, and I have never seen this. Let's see how it will fare and how people will use it.
Because, it's not about adding a new feature, it's about how people use it and if people use it the way they want them to use it then it would be a good job, but if people dislike it and abuse it and what not then it would create more problems for them than solutions.