Everyone I know who is on a carnivore diet has a high enough fat:protein ratio to stay in ketosis most of/all the time. The value of that seems to be pretty common wisdom among carnivores.
That said I have also done carnivore and also not been in ketosis, which I think is probably the norm for most people on carnivore because the protein/fat ratios aren't right.
The commonality in ketosis carnivore and non-ketosis carnivore is removal of refined sugar/carbs which means no insulin spikes, which means steady levels of energy without crashing.
The keto diet with ratios has been designed as a diet for epileptics, so in a ratio that maintains both body weight in a healthy range and induces ketosis and avoids ceizures (note: 1920s medicine or something). So the high fat content kind of is there to actually give you the energy so that you don't loose weight.
One aspect of the "carnivore" diet that is often overlooked, a "human carnivore in the stone age" will not have lived off of chicken breast and lean beef cuts, but easten the entire animal, i.e. the fat cuts as well that are surprisingly hard to get in a western country.
"White pasta" 40 ±5 vs. "Beef" 51 ±16
I think that the real question is "What will happen to my insulin if I eat a meal of pasta vs, a meal of steak?". To that, I think that the steak will in fact spike your insulin much higher than the pasta.
That said the beef has a higher satiety score (by almost exactly the same ratio as the high end insulin ratio).
Again, sauces, what your body needs right now, what you'll eat for your next meal,... lots of things can alter the overall health perspective.
As much as I think keto and carnivore are lightyears past the average American's diet, I've found them difficult to maintain because they're very restrictive and I lack the energy to be effective when working out, which is common. Fasting in combination with a low carb diet, even one that incorporates things like berries, has been much more effective and easy to maintain in my experience. Combining macronutrition with eating frequency reduces the penalty of eating carbs or lots of protein by making it much easier to get back into ketosis. When you force your body to burn through its glycogen stores, and you give it no choice but to use your fat store, ketosis will come back in no time.
So you are definitely correct that fatty cuts are better, most of the time, but with fasting the protein to fat ratio almost becomes a non-issue.
I found that I cramped, also. Eating 1/2 apple immediately before working out seemed to do the trick.