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There is no evidence the Sutta Nipata, Atthakavagga, Parayanavagga, Itivuttaka, Udana are earlier texts.
The Itivuttaka, Udana & many Sutta Nipata suttas (such as the Metta Sutta and Maha-Mangala Sutta) appear to be later texts.
The Atthakavagga & Parayanavagga of the Sutta Nipata were spoken to disciples of a Brahmin and contain very general simple teachings. Therefore, there was no need to mention nirodhi samapatti to these Brahmin students.
The older language used in the Sutta Nipata is similar to deciding to write poetry in Old English. The older language of the Atthakavagga & Parayanavagga is suitable for writing in verse (poetic style). Sujato has explained this many times.