Matsya Purana — Sādhāraṇa Śrāddha: General Ancestral Rite
पितृभिर् निर्मितं पूर्वम् एतदाप्यायनं सदा अपुत्राणां सपुत्राणां स्त्रीणामपि नराधिप //
pitṛbhir nirmitaṃ pūrvam etadāpyāyanaṃ sadā aputrāṇāṃ saputrāṇāṃ strīṇāmapi narādhipa //
O king, this rite called ‘āpyāyana’—the continual nourishment of the Ancestors—was established long ago by the Pitṛs themselves, and it is meant for all: the childless and those with children, and even for women.
Nothing directly about Pralaya; the verse focuses on Pitṛ-dharma, stating that the Pitṛs themselves instituted an ancestral-nourishing rite meant for all eligible persons.
It instructs the king (and by extension householders) that ancestral nourishment rites are a standing duty and not restricted by having or not having children—supporting the broader Matsya Purana ethic of sustaining lineage and social order through śrāddha/tarpaṇa.
The ritual significance is eligibility: āpyāyana (a Pitṛ-nourishing offering/rite) is sanctioned for the childless, the child-blessed, and women—broadening who may perform ancestral rites.