No, it has not been fixed, only reduced, VSync is still buggy and needs to be fixed. Please see my last comment.
It seems with RenderDragon VSync is completely messed up. If you disble VSync in the options.txt the lag gets worse, with the VSync disabled, if I enable "Radeon Enhanced Sync, the input lag reduces a bit, but the game gets choppy and there is some screen tearing, but only Enhanced Sync reduces the lag if VSync is disabled in options.txt. If I disabled the Enhanced Sync and enable or disable vsync, it doesn't do anything. If I enable VSync in options.txt regardless of Radeon settings, the lag reduces a little bit, but it's still bothers a lot. In the latest versions and betas which have smoother menu animations, the lag seems to be reduced a bit, but It's still worse than 1.16.100 and VSync is still messed up and needs to be enabled in options.txt.
In the 1.16.100 version, VSync options in options.txt and in the Radeon settings behave correctly and doesn't have the input lag, and if I disabled VSync in the settings file and in the Radeon settings I get a lot of screen tearing, but zero input lag.
This shows that the culprit for the lag and VSync problem is in fact RenderDragon.
Please Mojang fix the problem, make RenderDragon optional, or fix RenderDragon, I just can't play the game now, by now I have to downgrade the game using an unofficial launcher that I don't know if there are malwares.
This lag in the movement and in the space bar is very uncomfortable for me, it seems that my PC is not holding up the game. Please Mojang fix this problem, as I can't play the game with this lag. I use an AMD Ryzen 3 3200G processor with integrated Vega 8 graphics, and even though I disable vertical sync in AMD Software and in the game's options.txt, the lag continues. It seems that the only way to decrease lag is to activate "Radeon Enhanced Sync", but activating this option causes "screen tearing".
Lag is not bad at all, it's still present, but now the major glitch is that we can't get rid of VSync. Now there's no way to uncap FPS. VSync option is broken.