This profile pairs the third and fifth line positions of a hexagram, both of which carry settled readings in classical Yijing commentary that are unrelated to the names Human Design gives them.
What the commentaries say
The third line is the top of the lower trigram and a transitional position. The commentarial tradition characteristically reads it as difficult or perilous, poised between the lower situation and the upper and secure in neither. The fifth line is the centre of the upper trigram and conventionally the ruling position of the figure, the most favourably placed of the six.
The pairing therefore joins the least comfortable position in the traditional reading to the most authoritative one, which is a genuine contrast in the source material as well as in the modern system.
What Human Design does with it
The role names Human Design assigns to the six lines, and the reading of a profile as a personality, belong to the system and were published by Ra Uru Hu in 1987. They are not translations of the commentarial doctrine and should not be taken as a statement about Chinese tradition.
The pairing rule
Human Design uses twelve of the thirty ordered pairs of distinct lines, those separated by two or by three positions. The separations of three coincide with the Yijing's correspondences between lines one and four, two and five, three and six. This pair, separated by two, is not among them.