What is expected:

To be able to walk past 

What happens:

You get impaled on (check death message at the end of video) dripstone.

To repeat death (not 100% sure):

1. Set yourself to half a heart.
2. Place dripstone under a platform
3. Make a 5 block jump
4. Clutch using gravel and don’t jump just walk (however the video is the one exception)

(Note: Using Experimental Features (Vanilla Experiments), so that probably has something to do with that)