Assessing Differentiated Land Supply Performance Under China’s Major Function-Oriented Zone Strategy: A Scale–Structure–Efficiency Perspective

China launched the major function-oriented zone planning (MFZP) strategy in 2010 to address regional imbalances and resource–environment pressures through differentiated regulation. Using county-level data from 2010 to 2020, this study develops a “scale–structure–efficiency” framework and applies a self-organizing feature map (SOFM) model to examine construction land supply across four functional zones. The findings show that: (1) Key development zones provide the largest supply, while optimized zones supply the smallest but at the highest intensity, and restricted zones generally meet control targets. (2) Optimized zones record the highest incremental–stock supply index (ISSI), yet incremental supply still dominates; urbanized zones have balanced functional structures, whereas agricultural and ecological zones are more concentrated. (3) Supply efficiency in urbanized zones exceeds that of agricultural and ecological zones. (4) SOFM clustering identifies four distinct supply modes, reflecting regional heterogeneity in policy alignment. Overall, China’s differentiated land supply strategy broadly matches national goals, though some regions face excessive intensity and low efficiency, calling for tailored optimization measures.