Also, "Sheet Metal" vs. screw/fasteners......that "rusting" should be covered under these "Limited Warranty" items:
New Vehicle Limited Warranty
Sheet Metal:
• Corrosion coverage is for the first 3 years or 36,000 miles, whichever comes first.
• Rust-through coverage is for the first 6 years or 100,000 miles, whichever comes first.
...so, it might come down to whether they call it corrosion or rust-through.