Inner Steiner Pedal Ratios and Exceptional Zero-Area Families

For an odd-periodic elliptic billiard with a fixed nondegenerate confocal elliptic caustic, consider the polygon of caustic contact points and its own Steiner curvature centroid. We prove that this centroid is finite at every real phase and that the signed area of its pedal polygon is a phase-independent real multiple R of the contact polygon's area. Thus the reciprocal area ratio proposed as invariant k503 is constant whenever defined. Its denominator need not be nonzero: we construct a genuine convex five-periodic family in which the stationary pedal area vanishes identically, specifying its nondegenerate ellipse and caustic by a uniquely isolated algebraic root of degree 18. This is a correction to universal definedness, not phase variation of a defined ratio. The result includes odd coprime star windings under an explicit angle convention, odd repetitions, and a separate circle case. The analytic proof uses the pedal-area quadratic, elliptic-function poles and characters, and an odd quotient torus. Portable exact quadratic-field, symbolic-identity, and rational Bernstein certificates accompany the exceptional family. This is an unrefereed, AI-assisted preprint; no absolute priority, independent human review, or formal proof-assistant verification is asserted.