Command Block with auto:1b FallingSand Entity is not triggering.

How to reproduce:
Run the following Command:
/summon FallingSand ~ ~5 ~ {Block:minecraft:command_block, TileEntityData:{auto:1b, Command:/say HI}}
What I expected:
The Command Block will say HI upon touching the ground.
What actually happened:
The Command Block din't do anything.

(I'm not sure if this is a bug, but it seems to me like that.)