I think all this discussion is pretty stupid. It depends on the particular person.

You're generalizing too much. Ij means mental rigidity and nothing else. You can be rigid about an habit of being late, mean or whatever. You could say it's a virtue to fulfill promises, but it could also be seen from the perspective of not being able to move your schedule one bit due to your mental rigidity.

It would be far more interesting to discuss what makes two members of the same type so different. There are betas I dislike to the bone while there are others I admire.