My Dad made New England Boiled Dinner in a pressure cooker, with venison. There was so much grease on top of the broth that he had to skim it off. To emulsify grease, you have to have an emulsifying agent, like a base, or mustard, or egg yolk. The grease droplets will be made smaller. That is true. But it is still lighter than is the water, and doesn't combine with it. It floats to the top. And as for broths, they don't need to be clear. That's consume', and there are techniques used to make it clear. Broths must be rich in flavor and texture. And the nutrients from the inner parts of the bone do come out into the broth. Not all nutrients are damaged by heat. And in fact, in vegetables such as spinach, the nutrients aren't even available to the body until the spinach is cooked. Lima beans are poisonous until boiled. Many foods are actually more nutritionally sound after cooking. Son't take my word for it. Talk to a qualified nutritionist.
Seeeeeeya; Goodweed of the North