Ketosis and rabbit starvation (ammonia toxicity) are completely different things. The reason that there was too much protein in the meat was that there was not enough fat; carbohydrates are simply not available in Siberian winters.
Also, paleo diets don't aim for ketosis. Those are called keto diets, and for most people they're just a short-term rapid weight loss strategy (also useful long-term in epilepsy and possibly some autoimmune disorders). Paleo by contrast is supposed to be a long-term maintenance diet that usually doesn't aim for rapid weight loss.
Also, the downsides of "too much protein" have been well-known in pretty much every paleo discussion community since forever, since it's a well-known fact of experience among many athletes. The idea that protein toxicity is a problem in practice for paleo is silly (it wouldn't even make the top ten if you listed the real flaws).
I would not advise following paleo diets in the form they're commonly presented -- they place too much emphasis on the wrong things and contribute to the iconoclastic miasma that has been suffocating Western societies -- but the article's comparison is, nonetheless, completely off-base.
You’re absolutely correct that the Palio community tries to have sufficient carbs and fat to balance things out. However, I am basing this on what I observed people eating on Palio which while not correct likely does help the perception of effectiveness.
Actually, you would have to restrict your protein intake to small amounts to be in ketosis. It is very easy to get out of ketosis by eating a bit too much protein because it gets metabolized into glucose.