Answer:
Odysseus did not reveal the truth about Scylla because he knows his men will not row if they know how dangerous the situation is. In order to prevent that, he decided not to tell them anything about the danger posed by Scylla.
Explanation:
Homer's The Odyssey tells the story of the journey home of Odysseus and his men after the Trojan War. The journey also includes the various encounters that they had with gods and other monsters, who pose obstacles for the men.
In Book XII, Odysseus reveals the warning of Circe against the Sirens and the Wanderers, where Scylla resides. He told his men about the dangers of the Sirens' songs but did not reveal anything about Scylla. This, he mentions, is because "knew the men would not go on rowing if I did but would huddle together in the hold". He knows his men will refuse to budge and work if they know how dangerous Scylla is, so he rather chose to hide the information about it to them. This way, their ignorance about the issue helped them row on and move along the waves without any fear in their minds.