Any projectile thrown directly at the top of the dripleaf "leaf" part not colliding with the stem will cause only the top to break, leaving the stem topless, visually.

Steps to recreate:
1. Place a large dripleaf plant that is at least two blocks tall

2. Grab any projectile, I recommend a bow
3. Shoot/throw the projectile only at the leaf part's hitbox
4. If done correctly, the stem should be topless

5. Place a block where the top should be

6. You should see the top replace the block placed

(May take a few tries, as if you hit the stem hitbox of the actual leaf block, it will update the rest of the stem and it will fall)