There's still nothing there proving it's screen tear. Screen tear, which usually appears horizontally, is when frames of video don't sync. There's typically clear signs of it by seeing a distinct line where the frames are torn, often showing edges of objects shifting laterally vs aligned.
What you're showing instead looks like extreme lag and brief texture flickering, which could be due to low spec and/or driver problems. You've yet to even mention what spec you're running or if you have Vsync enabled. What I'm saying is just because a GPU says it supports Dx12, doesn't necessarily mean it supports it well enough to get any benefit from it. It can vary from game to game too depending on how well the devs implement it.
For instance my 7970 supposedly supports it, but it doesn't have enough ACE units to take advantage of it well enough to offer any performance improvement, and more often than not it results in worse performance, so I use Dx11 mostly, including in RotTR. As I said, I'm pretty sure Dx12 is mainly broken with one particular cutscene near the end of the game, but it's also not optimized very well for low level Dx12 capable GPUs.
Lack of optimization for older gen GPUs does not equate to broken though, especially with today's shoddily developed games.