Not at all. On this forum, for example, INTPs generally among the best at theoretical knowledge of typology, and among the weakest at actually typing people.
Of course, that's what you'd expect, theoretically...
I would be very cautious about making any inferences regarding an individual's personal qualities on the basis of their type. It is often very difficult to make such judgments without committing the Keirseyan fallacy. Essentially a temperament is merely a collection of an individual's natural tendencies of thought. Often times these tendencies entail behaviors, yet it is unclear what the precise frequency rate is. For example, Introversion often leads people to become quiet and reserved, yet there are introverts who have obnoxious and brash personalities. Similarly, an INTP set of dispositions may often lead a person to be uininterested in people and therefore perform poorly in determing their type, yet again, its unclear how often this happens.
We'd need careful empirical studies to answer that question. What would be necessary is a study that shows that people of a certain type in all scenarios tend to exhibit the same traits. As for instance, if INTPs in all sub-cultures of China, South Africa, Australlia, U.S and virtually all parts of the world displayed the behaviors you have in mind; we would be able to conclude that the temperament is a likely cause of the behavior. However, since we have none of such studies, we do not know if the INTPs you observed are poor at typing people because of their temperament or because of their extra-typological influences such as their culture or personal experiences. If the latter is the case, then your characterization is not describing a temperament, but merely socio-cultural personality features that are irrelevant to typology.
In short, the problem with the Keirseyan inference is that it asserts conclusions about the empirical world or about people and fails to provide a sufficiently rigorous justification. What would be necessary is a careful controlled empirical study as described above. Keirsey lacks this and merely claims that the 'behavioral sciences' such as anthropology, sociology and psychology have guided his insights. He offered us no reason to believe that this is true, the method of Please Undersand Me Volumes I and II are pseudo-scientific through and through.