The whole advice from grandma is nonsense. You probably have a wealthy background, but my grandma was poor, uneducated, and cooked meals based on what was affordable. That isn't advice, that's an economic condition.
The later, and current version of the guide influence institutional kitchens that do not have dedicated nutritionists such as daycares, some schools, clinics, etc.
If I followed by grandma's preferences we'd be eating canned food, salted meat, mincemeat pie, a lot of mayonnaise and cookies (exaggerating of course).