In dalalat al-nass, the meaning of the text extends to a case through a plainly understood rationale. The ban on saying “uff” to parents indicates a prohibition of more severe mistreatment through the understood harm involved.
Iqtidha al-nass arises when an omitted element must be understood for a statement to make sense or carry a legally valid meaning. Only what is necessary may be supplied. Dalalah extends the indicated ruling, while iqtidha supplies a required implicit element.