To reproduce
1. place cobwebs in a surrounding place /fill ~-20 ~ ~-20 ~20 ~ ~20 will do it.
2. Go on top of the highest cobweb and let yourself fall through it
3. Do /kill while falling through the cobwebs
Expected result
You fall through the cobweb as normal during the first second after death
Actual result
You fall through the cobweb much faster then normal for the first second after death.