IMO, Tri Tip is a lean cut of meat with very little fat other than most have a fat cap... At least round here they do. No need to worry bout the rendering on a TT ! It's a very lean cut that's much better pulled at IT of round 135-140* ! If a TT was taken to 200* IT, again IMO it'd be dry & crumbly !
Brisket has fat that has to be rendered to be tender, why you take it to IT to near the 200* mark. It's tough til the fat renders !
Hope this explanation helps !