This work reports empirical evidence for a universal realization drift characterized by a global frequencyΩ ≈ 31 nHz (T ≈ 373.36 days), which manifests selectively across physical systems. The drift does not correspond to a local oscillation, force, or dynamical field. Instead, it represents a slow phase evolution of the realization reference frame through which physical systems become observable. Using a unified and symmetric methodology, the study compares two classes of observables: Test A (Realized systems):Atomic clock ensembles and pulsar timing data reveal phase-coherent Ω-scale signatures when analyzed with fine-tuned period differentiation that separates T = 373.36 days from the calendar year. The signal is consistent across independent realizations and incompatible with local environmental or seasonal systematics. Test B (Completed structural boundaries):Black-hole structural observables—including horizon-scale geometry from EHT observations and long-term astrometric core stability—exhibit no detectable Ω-scale drift under identical analysis assumptions. This absence constitutes a positive null result, indicating that black holes behave as completed realization boundaries rather than dynamically realized systems. The work further demonstrates that this realization-drift interpretation is fully compatible with general relativity. Geometric descriptions of spacetime curvature remain valid, while realization drift provides a complementary structural explanation for why certain geometric quantities remain invariant while realized systems exhibit slow global phase evolution. Taken together, the results establish a sharp empirical distinction between realized dynamics and completed structure. The selective appearance of Ω across domains strongly constrains alternative interpretations and introduces realization drift as a new organizing principle for precision measurements in physics and astrophysics.