Minecraft monster trap built right?

Hi,

Built a monster trap in Minecraft. I knew them from before. Plenty of mobs also spawn, but they don't fall down, is that no longer possible?

Have an area of 100x100 blocks underground. 2 blocks high and water everywhere on the sides which flows into a hole in the middle. However, no mob falls into the water.

The water has to push the monsters into the trap for the trap to work.

Monsters are apparently more intelligent than they used to be.

On water: Water flows 7 blocks and monsters can't spawn in water.