Not much of a contradiction. Actually there's more than one interpretation on the "head" versus "heart" issue of the MBTI (in enneagram "head" triad types are 567, "heart" are 234). Some versions place the tendency to choose "head" as a mark of Rationality, which tends to be associated to Conscientiousness in the Big 5, which is the closest equivalent to MBTI J. This means a tendency to be more out of touch with spontaneous instinctual decision-making, which tends to be associated more with P, as well as spontaneous apprehension of relevant feeling, in favor of systematic thought.
For those who struggle with the fact that Jung seemed to have called feeling a
rational function it's safe to say the actual meaning is closer to saying that there is a rational basis for our feelings, than that reflective rationalization to Jung had no negative impact on feeling.
Jung said:
In the same way, thinking is opposed to feeling, because thinking should not be influenced or deflected from its purpose by feeling values, just as feeling is vitiated by too much reflection
In the modern instruments such as MBTI or Five Factor Model, some of Jung's typological phenomena are reorganized, and it's safe to say I think that the stuff I mention about Conscientiousness, rationality, and so forth subsumes some of what you associate to the brain/logic vs heart question.
Someone who's INfJ or INtJ might be pretty warm, caring, and so forth, but tend to have a lot of "head" energy, and might even be a purer head type like 5w6 or 6w5, rather than 5w4 or 4w5 which are more classic INFJ types.
Like [MENTION=2873]Serenity[/MENTION] has written, 6 wing, especially with a phobic touch to it, tends to go quite well with extraverted feeling. Among the defense mechanisms of these types is a combination of head energy to sort the so-called problem of knowing, certainty, and so forth, while recognizing deeply the importance of warmth and closeness and connection as part of handling anxiety.
I should note that I do not believe INfJs need to have extraverted feeling, as the relations between the Type Indicator and the Jungian theory are quite shaky, but in case you identify with it, the above is my take.
If you want to understand MBTI F in terms of the Five Factor stuff, I'd say that a good approximate to it is the Tenderness portion of the Big 5, coupled with various aspects where are more humane sentiment oriented.
It's also worth noting that in traditional enneagram, type 3 should be thought of as high in *feelings* but not high in
humane sentiment. The latter corresponds to MBTI F much more. Feelings in general can be more a property of being aware of the extraordinary and so forth. Lots of narcissists have a great understanding of various feelings, and plenty of narcissists probably are type 3 (albeit with an extraverted bias).