Duke certainly hasn't forgotten that one of the requirements for their assessment task was to submit a map of the Desert Lizardmen tribe, with annotations on the distribution of defensive forces.
In each Desert Lizardmen tribe, there exists a leader comparable to an Official Wizard, which is definitely an existence that the Wizard Apprentices cannot contend with at this stage.
However, Black Sail still asked them to create such a map, clearly not to destroy a Lizardmen tribe, but merely to test their reconnaissance abilities.
Duke had already reached a consensus with Simon and the others: they must not attract the attention of the Lizardmen tribe, nor could they get too close to it.
With their strength, if noticed by the Lizardmen leader, they probably wouldn't even be able to escape.
The more prudent way is to keep a certain distance while completing the map drawing.
Abel is obviously the best candidate for this task; his Eagle Eye Technique is just for reconnaissance work.
