The questions are designed to elicit the strengths and weaknesses of candidates. While our type indicates our predisposition towards certain strengths, this does not limit us. The questions focus on whether the candidates have developed their strengths, whether they are aware of their weaknesses, and have they taken steps to compensate for them. The questions are excellent and are likely to get at the heart of any limitations and to find out if the candidates are aware of these weaknesses and have attempted to compensate for them.
For example, ESTPs might be asked to give an example of when they acted on impulse, what were the results, and what action were taken to monitor this impetuous behaviour. Another example might be INFJs being asked to describe an incident of having to deal with difficult people to work with, and how the situation was handled.
I can see these questions being very valuable to the interviewer as they tend to zero in on the limitations of each of the types. I have a question about the ethics of using the questions in this way. As I understand it, MBTI® instrument results are to be only be given back to the person taking the indicator. To be able to use the appropriate set of questions, the interviewee would have to divulge his or her type. Of course, the interviewer is quite free to guess the type of the interviewee and then ask appropriate questions. The book itself is quite useful as a selection of questions to ask in relation to the needs of the specific position.
On the other hand, the questions are very valuable to a person being interviewed. Being forced to look at the most likely areas of weakness is a necessary exercise for anyone aspiring to leadership. The questions would also be very good ones to use in a leadership seminar.