Parameter choice Supersingular Isogeny DH
Found the answer:

The $l$-torsion subgroup is isomorphic to a direct sum of two quotient groups:
$E[l] \simeq \mathbb{Z}_n \oplus \mathbb{Z}_n$, hence the basis requires two points and the elements of $E[l]$ are represented by linear combinations of such a basis.
[Reference: Elliptic Curves, Washington, section 3.1]