What I expected to happen was...:
When using command

/summon FallingSand ~ ~3 ~ {Block:minecraft:log,Data:4}

the block 3 blocks above the command block should turn into a log facing east/west and wall and land on the command block.

What actually happened was...:
When command previously stated is used the block turns into a log facing up/down until it hits the ground and then faces east/west once the block has actually been placed.

Steps to Reproduce:
1. Place a command block with the command stated previously
2. Place a log with any data value 3 blocks above the command block
3. Use any kind of redstone to activate the command block

Edit/Note
I went back and tested this in 1.7,2 (because I was almost 100% sure that the fallingsand logs were behaving properly in that version) using the command:

 
/summon FallingSand ~ ~3.5 ~ {TileID:17,Data:4} 

and something similar yet different occurred. The logs themselves oriented correctly but the bark was still orientated vertically. I'm not sure if this information is helpful but I thought I would add it.