Agreed, it does sound that way, but it's amazing how many anecdotes there are of people who eat exclusively 1 type of food and thrive on it. I don't think modern intuition about nutrition is likely to stand the test of time.
The conclusion I have come to is that humans, when starting from an over-fed modern baseline, are robust enough to eat a totally shit diet for a couple months. This is also long enough to convince us it is worth blogging about.
The subculture of long-distance hikers who optimize by going fast and light (maybe 1-3 lbs food per day plus 10-20lbs of gear). They'll go for months on extremely weird diets that optimize for calories per gram while doing more exercise than they've ever done and generally be fine.
I've only heard that about carnivore diets, and it makes sense to me. Where can you find all the nutrients necessary for a mammal to survive? In the body of another mammal, of course.
