yes and no, if they fail to find a spawn node as a scout, they'll try as a non-scout instead, and vice-versa. there's some percentage of how many aliens on average will be scouts and how many won't, defined in the deployment rules.
so for example on a crashed battleship, the commander will always spawn in the control room, the terror units will spawn in the corridors near the lift, engineers will be in the engine rooms in the feet, and so on. some % of each rank (plus any that couldn't find a ranked node) will use rank 0 nodes instead, and spawn outside the ship.
basically, put ranked nodes in the ships, and unranked nodes in the terrain.