As your customer, I am not complaining, but I hope you can be better.
I think this should be considered by the provider as a theme solution.
You provide an intranet solution without considering access issues. How can users use this theme to solve their problems?
If themes don’t solve their problem, why buy a theme?
If the forums under the private group are also privately accessed, this is a bbpress feature. Well, as a theme solution provider, at least from the perspective of selling the theme, you should also test it to see if this can be solved. If it can be solved, this will be able to solve the needs of users and is a selling point of the theme. If this is not possible, the customer can be clearly told that it is not possible. Avoid customers wasting time.