Matsya Purana — Ekoddiṣṭa Śrāddha
सपिण्डीकरणादूर्ध्वं प्रेतः पार्वणभाग्भवेत् वृद्धिपूर्वेषु योग्यश्च गृहस्थश्च भवेत्ततः //
sapiṇḍīkaraṇādūrdhvaṃ pretaḥ pārvaṇabhāgbhavet vṛddhipūrveṣu yogyaśca gṛhasthaśca bhavettataḥ //
After the sapiṇḍīkaraṇa has been performed, the departed (preta) becomes entitled to a share in the ancestral offerings of the monthly śrāddha (pārvaṇa). From that time onward, he is fit to be included among the ancestors in vṛddhi-type śrāddhas performed for auspicious increase, and is thereafter regarded as a gṛhastha, a settled member of the ancestral household-line.
This verse does not discuss Pralaya; it focuses on post-death ritual law, explaining how the preta’s status changes after sapiṇḍīkaraṇa so he may receive ancestral offerings.
It supports gṛhastha-dharma: householders must perform sapiṇḍīkaraṇa and subsequent śrāddhas so the departed is properly integrated among the Pitṛs and included in regular (pārvaṇa) and auspicious (vṛddhi) ancestral rites.
The significance is ritual, not architectural: sapiṇḍīkaraṇa is the key rite that ends the preta-phase and grants eligibility to partake in pārvaṇa offerings and be included in vṛddhi śrāddhas.