Electromigration is a key reliability issue in VLSI interconnects, where copper is being replaced by tungsten silicide (W-Si) and ruthenium (Ru). Experiments show EM-induced voids in W-Si and Ru at sites opposite conventional electron wind force predictions, sparking hypotheses of hole-dominated transport and p-metal behavior. This work provides a consistent explanation using density functional theory with atomic flux divergence analysis, demonstrating that hydrostatic stress gradient force dominates void formation, independent of effective charge number (Z*).