Desync with taking damage from jumping off the iron trapdoor

I found a bug where the game thinks that I fell down, although I still remain on the platform, I found the bug a long time ago, since version 1.20.10, but maybe even lower

 

Link to video footage where I showed everything in detail: https://www.youtube.com/watch?v=eD_PHJ-CdWY

 

How to make this bug?

 

1. you need to rebuild the structure like in my video and screens(below)
2. it is important to know that in the 3 by 3 water there must be a block on which the game will think that we are imaginary jumping
3. and now its only your reaction time
4. u can do it without water, but i think, that you can catch timing much more often when there is water below