Totality of circumstances suggest these are far from your friendly kobolds. It would be a potentially mind-blowing experience if by some off chance they were and just so happened to be following such an army, or eve on the same path. Now in a normal game with a Dungeon Master who is fond of this sort of "trickery", to put it kindly, that I could potentially believe. But a module? Even if it were an older one, that is a trap they would consider too brutal.