FallingSand with TileID:2 grass block has grey top texture while falling.

Using a command block, when a FallingSand block uses a TileID:2 to make it a grass block, as it falls, the top side is grey in color until it lands. I tested with /summon FallingSand ~ ~2 ~

{Time:1,TileID:2}

but the coordinates can be anywhere where the sand can fall.