Maybe he'* referring to trapping moisture underneath? If it'* a good uniform plating on properly prepped base metal, it'll last for years. Until you get your first fender-bender and expose it to air. Rust on steel is oxidization. It needs air to do it. No air, no rust. Think of the plating as the 'air shield' for the metal underneath. Let air in, and a little moisture in a protected environment, and it can rust undetected for years.
For work applications if I need a plating, I generally go with nickel. It'* softer, and more likely to be misshapen rather than crack. Nickel isn't nearly as brittle. A uniform nickel plate on an aluminum part gives it alot more surface strength and abrasion resistance than anodizing.