Oh, Hi, RansomedbyFire. Welcome to MBTI Central.
Anyway, as far as I can tell, it means all their functions are focused in the same directions in terms of Introversion/Extraversion. We aren't sure theoretically what this means, but it could mean that despite having different personalities, these types understand each other on some level for this particular reason. I've noticed a lot of people seem to marry/befriend those who have their tertiary and inferior as dominant and auxiliary, but I'm not sure if that's significant.
It would be easier if we could confirm the functional orders somehow, but we're dealing with intangibles here, so nothing is certain. But if Jung's model is correct, those orders are accurate. We should probably do some kind of research to analyze the impact of having all functions in the same direction on the I/E axis, versus having them in different directions on that axis. Some might have already been done, but I'm not aware of it.
Anyway, this was very insightful, and may have given us a new perspective from which to analyze intertype relationships.