This study provides a self-consistent first-principle interpretation of the persistent proton radius anomaly under the framework of Boundary Interface Theory. Based on the four-dimensional normal direction structure and topological knot model, this paper clarifies that the systematic radius deviation stems from different structural sampling layers of protons caused by the inherent standing wave layer difference between electrons and muons. The same theoretical system unifies the essential mechanism of muon weak decay, which is fully in line with verified experimental results. Both English and Chinese full-text versions are permanently archived for open sharing and long-term bibliographic retrieval.