I doubt that this is true. In the era of colletion and hunting, the diversity of food is based on the near-by ecosystem, which is larger than modern supermarket.
Meat? tons of variety, there are like twenty different cat to dog sized animal species in my Montana wilderness before I even have to get to the large herbivores that have less variety. And meat is special anyways, the mink or weasel you can kill is chock-full of 2-5 years worth of collecting resources from various animal and vegetable sources.
Pine needles "contain more Vitamin C than an orange" (I didn't see it specified if that's by gross weight or dry mass) and make decent tea, and many cultures still boil and eat or cook with pine cones.
Modern crops are amazing, but we are literally surrounded by new and forgotten sustenance. It's not always pretty, tasty, or toothsome, but it's there if you have the time and will to turn it into food.
I'm also reminded of villages that "modernized" by trading their old fashioned cast iron cookware in for aluminum and began to suffer from anemia as a result. Iron is abundant in the crust, and eating mineral-rich clay is still practiced by humans and animals around the planet, but their solution was to put cast iron charms in the new pots for luck. It's possible they were in iron-poor areas, but if they were swayed to abandon their traditions by the appeal of commercial marketing, it seems likely they mught also eschew any dirt-eating practices they once might have had.
Hadza ate only 4 non-animal foods, which is much less than what's available at a supermarket.
Hunter gatherers would've had a more diverse diet when it came to meats, eating the entire animal including most organs, but that's more cultural than what's specifically available at the supermarket (it's pretty easy to get organ meat at the supermarket and especially the butcher, but most people don't opt-in).
Other parts of the animal, like the liver, would provide sources for A and B12, etc.
> Because of its content in highly valuable
> nutrients such as iron, zinc, selenium, fatty
> acids, and vitamins, meat is a unique and
> necessary food for the human diet in order
> to secure a long and healthy life, without
> nutritional deficiencies.[2]
[2]: https://www.sciencedirect.com/science/article/abs/pii/S03091...