To answer the OP original question.
There is no scientific evidence to support the theory of primacy as applied to learning/training in general.
It's interesting that someone mentioned the MBTI because Jungian theory posits that only certain personality types are subject to primacy; namely, the sensing type.
On the other hand, Freudian theory states that primacy is primary an age-related issue and that under stress people will revert to childhood.
Personally, I think that primacy or reversion under stress is a lot of psychobabble. The claim that first impressions are inedible impressions has little scientific evidence to support it either in the field of education or psychology itself. To the extent that primacy has scientific support it's usually on the basis of efficiency, not effectiveness. That has little to do with pilot training.