Y'all are acting like this is some NEW thing...
Brake lines have been rusting out on vehicles ever since there were brake lines. GM has only ever used cheap steel lines.
Dad's owned a 1973, a 1978, a 1989 and then a 2000. He has had a brake line failure on every single one of them, and had to replace the brake lines because they were rusted out.
Even my 2002, which as never seen road salt, had the brake lines rust out on it last year, so for you who live in Arizona and think you're safe... Think again.
Stainless brake and fuel lines should be MANDATORY.