That one ant going the "wrong way" isn't less intelligent than the rest. She's an essential part of the system.

Because sometimes that ant finds a shortcut. If she finds a short cut the pheromone path and even the passive evidence of her motion, the freshness of the leaf bit she delivers will attract more ants to her path. Quickly, without discussion or resentment all of the ants switch to the new shorter path.

The wrong way ants prevent the ants from being trapped in bad attractors.