Do grill covers cause rust or mold?

This is a real, repeatedly cited downside. High-trust community threads warn that fully waterproof covers can trap condensation, leading to mold or rust if a grill is put away warm or stored without ventilation. Covers with mesh air vents and a snug-but-breathable fit are widely recommended to let moisture escape, and several reviewers suggest letting the grill fully cool and dry before covering.