What im doing was:
1.Play Minecraft
2. Make a new world
3. go to a good spot in the jungle biome
4. do /fill x1 y1 z1 x2 y2 z2 minecraft:air 0 replace minecraft:leaves 3 and log 3
5. Everything disappear (except the grass,stone, and other stuff that's not selected)and vines will fall

What i get instead was:
1.Play Minecraft
2. Make a new world
3. go to a good spot in the jungle biome
4. do /fill x1 y1 z1 x2 y2 z2 minecraft:air 0 replace minecraft:leaves 3 and log 3
5. Everything disappear (except the grass,stone, and other stuff that's not selected) but this time, the vines just flying in the air! (it'll change disappear if you place the block on the side of the vines)