I'm not sure if I'm wrong, but it seems that you take too long to take the actions. I mean, while you have target button pressed it doesn't matter because the warp is not loaded in memory, but when you release target and change your camera the warp is loaded for a few frames.

I see in the video you went to the wall and targeted that wall 2 times, an dthe first time you untarget, waited like 2 seconds and retarget. Try to do it faster, untarget and retarget the wall fast, don't do it 2 times, and change the direction fast again.

Also, don't release Z to open the door, I do not release it never and it work for me every time, if you do it fast enough it shouldn't matter, but just for safety...

Again, maybe I'm wrong but everything else looked fine to me in that video.

Because they do not reset the game.

For the WW the last cutscene seen is important as SnipinG said, if the last cutscene seen is the enter the deku tree for the first time it will work. But if you reset the game completely then it wont work. Anyway, if you had the black screen with noises that means the WW was correct, now you only need to go to Link's house and pause the game and try it again, or just start a new run and do not restart the game after the cutscene of enter the deku tree.