I think we have to be careful, Stefansson didn't meet all of the Inuit/northern native groups. Also there are non-liver food sources of vitamin A the Inuit ate that we don't. Nutrition data gives 100 grams of Beluga whale, that's about 100 calories, as 7 percent of daily vitamin A requirement, so at 2000 calories that would give 140 percent. But that's a ridiculous 100 percent of calories as protein. If you assumed 30 percent protein, that goes down to 40 percent requirement for vitamin A. You could probably fluff that up, there are accounts of very high food consumption by traditional Inuit, not exactly a sedentary lifestyle. Also, like grassfed meat vs. conventional, the herbivores eaten are likely to have fat richer in beta carotene Liver isn't an essential food, the nutrients in liver are, we can't assume that the Inuit didn't need liver, so we don't. We don't know that all groups didn't need and didn't eat liver, and we don't know that they didn't make up for the lack of nutrients from liver in other foods that we don't have access to.

Understand that I'm not arguing that we must need liver, just that there's uncertainty here.