The short answer
According to the definitions provided, the reason that a thorny problem does not have a stop rule is that it usually allows a stop rule to be applied to a problem because there is an acceptable or optimal solution that allows you to reach a point where it is not necessary to continue to search or browse a better solution.
I suppose that means that you do not really know if you are dealing with a thorny problem, but you will know if you are not dealing with a thorny problem, because you will have found a solution to this problem. The problem is that it is sometimes difficult to say if the lack of a clear solution is due to the fact that you have not solved the problem correctly or if it is simply a thorny problem that you face.
If you have the impression that the problem you are solving seems to be a symptom of another problem, and that there might be a clash or a circular relationship, it might give you an indication that you are dealing with a thorny problem . Other times, you may simply miss an important piece of information and, therefore, you may not be able to integrate it into your solution.
A typical problem is behavioral design involving people facing resistance or adaptation to change. For example, if you are creating a solution to a behavior problem and find that the user group is simply changing its behavior to create another problem, and that each new solution generates a new problem, you are potentially faced with a problem thorny. However, it may also be that you have not necessarily addressed the root cause of the behavior problem, or that it is subject to random or unpredictable forces, which prevents you from finding a way to solve it. integrate into the solution.
Nevertheless, this does not prevent people from trying to solve such problems because, as I already mentioned, you do not always know when you are dealing with a thorny problem, and it is in human nature to continue to try when they think it's worth it. time and effort (or sometimes because they have already invested a lot of time and effort).