Most suttas about Anupadisesa Nibbana give the impression (Iti 44) or literally say (Iti 112; AN 4.118; AN 8.70; DN 29; MN 140) that Anupadisesa Nibbana (nibbana without residue'/fuel/remainder) is the permanent ending of the life & consciousness of an Arahant.
However, AN 8.19 and Ud 5.5 about the Great Ocean say:
(5) Just as in the great ocean neither a decrease nor an increase will appear though all the streams of the world flow into it and rain falls into it from the sky; even so, even if many monks attain final Nibbāna in the Nibbāna element that is without residue left, there is no decrease or increase in the Nibbāna element that is without residue left. This is the fifth wonderful and marvellous quality in this Dhamma and Discipline….
https://www.bps.lk/olib/wh/wh208_Nyanap ... I.html#T96
Just as, monks, the streams in the world flow into the great ocean, and showers fall from the sky, but it is not known that there is a depletion or filling of the great ocean by that, so, monks, even if many monks, are completely emancipated in the Emancipation-element which has no basis for attachment remaining, it is not known that the Emancipation-element is either depleted or filled by that. That, monks, even if many monks, are completely emancipated in the Emancipation-element which has no basis for attachment remaining, it is not known that the Emancipation-element is either depleted or filled by that, is the fifth wonderful and marvellous thing, monks, about this Dhamma and Discipline, which, having seen and considered, the monks delight in this Dhamma and Discipline.
https://suttacentral.net/ud5.5/en/anandajoti
Why would the suttas mention (wrong) ideas about the depletion or filling of the Nibbana Element if Anupadisesa Nibbana only related to the ending of the life of Arahants? In other words, obviously nothing occurs when the life & consciousness of an Arahant ends. Thus, why would AN 8.19 and Ud 5.5 even discuss this potential question; unless it was the notion that Nibbana attained during life returns back to the source of Nibbana?In the same way, though several mendicants become fully extinguished through the natural principle of extinguishment, without anything left over, the natural principle of extinguishment never empties or fills up.
https://suttacentral.net/an8.19/en/sujato
Thank you. Please discuss.