He notes no mods in the description of the video - intake/exhaust aren't going to be in play here unless the dealer/Toyota is an absolute stickler...I'm quite sure TRD sells the same type of mods which are warranty-kosher. Based on teh fact he even mentioned the track use or showed this video to Toyota indicates that he likely isn't hiding anything (who does that?).
Spend 5 minutes Googling "GR86 oil starvation". Huge posts on the 86 forums about it, on the main car sites, etc.
I agree with your last statement but if you can't drive like he did on the stock setup, that's an issue that would present itself more regularly on the street. I do some mountain cruises with folks in the same car that push harder than that. The most likely speculative scenario is the RTV blocking the oil pickup here, not BITOG 20W boogieman (I mean now even 30W isn't enough for driving harder than a grandma on BITOG?...good lord), driver, mods, etc.