Split shot takes 2 or 3 tiles, not one, and it is a ranged attack, not melee.
I was thinking about the issue of this being a stoppable attack, and I think that the best way would be "no": an obstacle in front of a spearman shouldn't really prevent him from attacking an enemy on a free adjacent tile via a tile that's also, most likely, obstacle free.
OOO
EXO
OSO
O=empty
X=obstacle
E=enemy
S=spearman