Do a google search on rusty nails with OC laminate shingles, you'll find some.
Seen a half dozen or so reports in the past couple years and finaly saw it first hand. Couldn't get a name on the coil nails but they look a lot like what I've been using over the past 6-7 years.
Drop a coil of nails in water and it will rust. Not right away but it will rust. The only nails that won't rust with constant contact with water would be copper or stainless steel.
That's odd that Certainteed would allow a big box store to sell there shingles. In print Certainteed there shingles are builder and professional grade and not sold in big box stores as a result.
I know Menards sells Certainteed siding but although it can order in Certainteed shingles they are not stocked.