Nezha wouldn't reveal his task of searching for the Hongmeng Purple Qi. It wasn't out of fear of the Queen Mother having ulterior motives, but rather apprehension regarding Hao Tian. It's not that Hao Tian is inherently bad—Hongmeng Purple Qi is something everyone desires, and as someone who was once Daoist Ancestor's disciple, Hao Tian especially understands its significance.
Until the very last moment, Nezha wouldn't share this matter with anyone—not even Daji and the others. This was his way of protecting them.
Nezha instead talked to the Queen Mother about how No-Life Old Mother had intercepted him at Lingshan and how he later pursued her to the True Void Home, assisting the Taiyuan Saint Mother in reclaiming No-Life Old Mother's origin.
