The entire video is important, showing off in great detail and breakdown of the issue at hand, and how we fixed it, all information I felt was relevant to this issue, despite having a modified game client which doesn't effect the issue at all, since anyone who's played Minecraft in the last 8 years knows the screen always tilts towards the left when taking damage, I assumed this was common knowledge. That is why I didn't bother running later versions of Minecraft in pure vanilla, but showed off version 1.2.5 in vanilla, showing where the directional damage screen tilt actually last worked.
I also explain in the video that this only ever worked in single player, never online. But due to the internal server change 1.3 added where single player now runs as an internal server, that bug from multiplayer was transferred to single player.
Everything is quite explained in the video.
There is footage later on in the same video showing it off in vanilla.
Is there any reason given why it's resolved as "won't fix"? And are we sure it was actually the official developers themselves who marked it this way? Looking at the original ticket, it still shows as "unassigned", and doesn't say exactly who resolved it. Mojang has also changed quite a lot over the years, it's possible this is something they'd like to fix now, if it gets brought to their attention properly. Again, the code for this is still in the game, all the way up to 1.16.3.