That first study compares to meat-containing diets with each other, see the methods section.
edit: I also have some doubts on the care taken in this study and it's peer-review. As there is an easy to spot mistake in table 2 (the dietary fat section).
Studies on human nutrition are extremely limited. If you'd like to see a case reports about keto eating putting Diabetes Type 2 in remission see below:
https://www.healthline.com/health/diabetes/carnivore-diet-fo...