5 is the least integer admitting, on one element set, two mutually irreducible directed Hamiltonian cycles (steps 1 and 2); hence the "five" of the Five Phases is fixed by number theory.

Restraint = generation²: on ℤ₅ the overcoming map is the square of the generating map.

5 ∤ 2ᵏ: the Five-Phase track cannot be reduced to a binary (yin-yang track) representation.