Yes, afflicted planets with saturn in 6/12 can cause imprisonment because 12th is prison. But that is not the jaimini imprisonment yogas which are not based on house meanings at all but in how the energy flows through the chart. You may want to listen to the audio courses on that book.
Do you have any suggestion what useful advice can be given to people with bhandana yoga (jaimini kemadruma yoga)? You cannot just say "you are stuck, you will be, and will always feel to be"? You just ask them to accept what is, that is all?
How can we provide some hope and some ray of light to people with this combination?
To soften it a bit, one can use ‘Intense focus in one area of life’ instead of ‘Being stuck’. Unfortunately, it is only a sugar-coating on a bitter pill. It is being stuck, and one can’t do anything about it. It is an energetic prison, and all one can do is appreciate the small amount of leeway allowed and the lack of distractions so that we can focus on our individual consciousness in that particular area of life. I guess depending on other factors, either it will be a comfortable enjoyable prison or an uncomfortable painful one.