Well, that's a question of perspective, isn't it. For me, perfect health is the lack of disease or infection or disability of any kind. As far as I can see, the Bellevue experiment showed exactly that. But if you want to argue the opposite, please provide us with an equivalent experiment with plant matter only.

Health was measured in the experiment. It so happens that there was no indication whatsoever that any ill effect had occurred as a result of an all-meat diet. How do you quantify that level of health if not perfect? Half-perfect implies failing health. There was no such thing. Almost perfect health implies still a failing health somehow. There was no such indication. Thus, health was perfect for the duration of the experiment. There is no hyperbole. It's just a matter of fact. Their health was perfect as far as we can measure.