Okay, so the script will grab the initial movement for an NPC. You're right, it should return true if the npc is walking, but the problem is that the npc has two phases - Walks and stops. If the npc has stopped moving when the script is writing about it it will return false which is wrong.
So, if the goblin is stationary when the script finds it it will return false, and if one goblin is active when the script finds it it will return true, whereas we know, all goblins move. Is there any way we could actually check if the npc has walked in a given time and if not, it would return false.