Whole-plant foods vs whole plant foods

Hello and thank you all in advance.

Here's my sentence: "Many studies show the health benefits of complex carbohydrates consumed in whole plant foods."

And, so, I'm wondering whether "whole plant foods" requires hyphenation. My not-very-confident hunch is that it should be hyphenated because "whole plant" is serving as a compound adjective to "foods;" i.e., whole-plant foods.

That being said, there have been many times that I've seen the phrase, "whole food, plant-based diet." I'm not sure why the "whole food" in this example would not be hyphenated, while "whole-plant" may be in the first example.

Is my hunch in the first example incorrect? Or are people incorrectly omitting a hyphen when writing "whole food, plant-based," as in the second example? Or, finally, are these examples crucially different in some way that I'm missing?