The Structural Complexity Lab is a deterministic, interpretation-only observational framework developed as an extension of Structural Eligibility Screening (SES). This work establishes prior art for a system that distinguishes traditional contract complexity signals—such as page count, clause count, cross-references, schedules, amendments, and party count—from structural complexity, defined as a behavioral property arising from deterministic structural primitives, rewrite operator behavior, and SES eligibility classifications. The Structural Complexity Lab operates exclusively on deterministically enumerated scenarios and authoritative SES outputs. It does not perform prediction, optimization, scoring, valuation, risk assessment, legal analysis, or financial modeling. All outputs are descriptive and observational only. The lab processes 60,000 deterministically enumerated structural scenarios and compares metadata-based complexity descriptors with structural complexity metrics derived from SES classifications. Observational results demonstrate that traditional complexity signals function as surface-level metadata and are not determinative of structural behavior within the observed dataset. Structural complexity is shown to be independent of contract length, clause count, or other surface features. This publication is presented as defensive prior art. No patent rights are claimed. The system is non-predictive, non-optimizing, and non-advisory. All findings are deterministic, reproducible, and interpretation-only.