Tri tip was, and still is, ubiquitous on the West Coast. Packers briskets were hard to find, but TTs were everywhere. I've been grilling them since the early 80's, often 2-4 at a time, rarely just one. When my athlete kids were home, more than one disappeared at each meal.
I ALWAYS cooked them to rare or med-rare. Then, in 2018, a friend of the family grilled one to a med-rare temp, then finished it in the oven to 165°F IT. I expected shoe leather, but tasted melt-in-your-mouth brisket-like meat. I could not explain it.
Soon after I read a thread on SMF about taking TT to a higher IT, like 195°F. I bought two TTs on sale ($3/lb), grilled one to 165°F, wrapped the other and took it to the 190°s. I can't even begin to express how foreign and uncomfortable it felt to do both. The results blew me away. Both were tender, juicy, and different from each other. The 165°F TT was like a tender roast beef. The high IT was like the juiciest brisket flat I've ever tasted.
Do I still do it? No, because I can get packers easily now. The price of Choice and Prime TTs have climbed to a level I won't pay, but untrimmed Selects can still be found on sale for $3 to $4/lb, less if you buy the 5-6 piece bulk pack. They are still juicy and tender. We grilled one last week for fajitas.