finishing temp's ... grilling vs smoking vs USDA recommendations

Brisket gets tender over time because you're rendering the fat inside it. When you're grilling the meat isn't on the grill long enough to render.

Regarding USDA temps I think it's important to differentiate the different meats. When you're cooking a solid chunk of beef the internal portions of that meat should be aseptic and it should be safe to cook it to whatever temp you want - assuming it was processed, handled and stored in a safe manner. Hamburger meat that you grind at home can be treated the same way but I won't order any hamburgers cooked less than medium when I eat at a restaurant because I don't know how well they take care of their hamburger meat.

With chicken my understanding is that salmonella is present in a very high percentage of the chicken population and it permeates the cells after the chicken dies. So the meat doesn't stay sterile on the inside like beef. Pork can actually be cooked medium I believe because the parasite that causes the problem dies at this temperature. I think it's 150ish. As long as you hit that for a few minutes it's supposed to be fine. I'm not one to take chances with intestinal parasites so I'll go medium well on pork.