There may be something else in play: carb consumption. If you are 90% carnivore, you eat very few carbs per day, and lots of protein. If you are vegan, it is possible to eat rice and vegan muffins and croissants all day. (The vegan muffins I tried from whole foods were some of the sweetest things I've ever eaten. The vegan croissants I had from WF used margarine and didn't taste anywhere as good as the butter croissants.) So a vegan diet can definitely be less healthy than a omnivore diet.

I think if you are vegan and ate 90% tofu / pea protein / rice protein products, and spent the rest of your intake on avocados and olive and coconut oil and almonds and pecans, you might also look and feel great.