As an English scholar (who is often overmatched in scientific arguments on these boards), I would have to agree that the very word "pair" carries with it an implication of closeness, or appropriateness, that goes beyond just "two." From dictionary.com:
pair Audio pronunciation of "pair" ( P ) Pronunciation Key (pâr)
n. pl. pair or pairs
1. Two corresponding persons or items, similar in form or function and matched or associated: a pair of shoes.
2. One object composed of two joined, similar parts that are dependent upon each other: a pair of pliers.
3.
1. Two persons who are married, engaged, or dating.
2. Two persons who have something in common and are considered together: a pair of hunters.
3. Two mated animals.
4. Two animals joined together in work.
4. Games. Two playing cards of the same denomination.
5. Two members of a deliberative body with opposing opinions on a given issue who agree to abstain from voting on the issue, thereby offsetting each other.
6. Chemistry. An electron pair.
As you can see, though it's not linguistically perfect, anyone selling a "pair" is clearly implying some kind of relationship. Specifically note 3-4.