Is killing an enemy scout considered a battle?
No. If you aren't drawing square unit cards, a battle isn't taking place

From the FFG rule book (page 23)


  Battle is the struggle of one civilization against another for dominance. When an army figure moves into a square containing a village marker, an enemy army figure, or an enemy city, a battle takes place.


If you had continued reading the section ENEMY FIGURES, you should have realized that.


  Scouts cannot enter a square containing enemy figures. If an army enters a square containing any enemy figures, its movement immediately ends. If the square contains only enemy scouts, the scouts are immediately killed and the attacking player collects loot as though they had won a battle (see page 25). If the square contains at least one enemy army, a battle occurs (see page 23). If the square contains a mix of both enemy armies and scouts, a battle occurs, but if the losing side in the battle has any scouts in the square, they are killed along with the armies; loot is then collected as normal.