I am examining the stock definition of a Non-Returner, as follows:
Following the various Sutta Central links to the term "parinibbāyino" finds:In this Saṅgha there are mendicants who, with the ending of the five lower fetters are reborn/arisen spontaneously. They are extinguished there, and are not liable to return from that world.
Santi, bhikkhave, bhikkhū imasmiṃ bhikkhusaṃghe pañcannaṃ orambhāgiyānaṃ saṃyojanānaṃ parikkhayā opapātikā tattha parinibbāyino anāvattidhammā tasmā lokā—
aor. of parinibbāti
pari + ni + vā + a
to be completed, perfected in any work or art, e.g. of a trained horse MN.i.446.
pp parinibbuto (q.v.). Caus. parinibbāpeti (q.v.).
to bring to complete coolness
pari + nibbāpeti
completely calmed, at peace, at rest
pari + nibbuta
pari + nibbāna
ni + vā + e
pp. of nibbāti
Although I am unable to distinguish the words above, SN 6.15 & DN 16 appear to distinguish between 'parinibbāyi' & 'parinibbānā', where 'parinibbāyi' might be a verb and 'parinibbānā' is an event/noun:
The word 'parinibbāyati' is found in many suttas refering to here-&-now Nibbana:Then he entered the fourth absorption. Emerging from that the Buddha immediately became fully extinguished.
Catutthā jhānā vuṭṭhahitvā samanantaraṃ bhagavā parinibbāyi.
When the Buddha became fully extinguished, along with the full extinguishment, Brahmā Sahampati recited this verse:
Parinibbute bhagavati saha parinibbānā brahmā sahampati imaṃ gāthaṃ abhāsi:
Meditating in this way, they don’t grasp at anything in the world.
So tāsu vedanāsu aniccānupassī viharanto, virāgānupassī viharanto, nirodhānupassī viharanto, paṭinissaggānupassī viharanto na kiñci loke upādiyati.
Not grasping, they’re not anxious. Not being anxious, they personally become extinguished.
Anupādiyaṃ na paritassati, aparitassaṃ paccattaññeva parinibbāyati:
A mendicant free of grasping becomes extinguished.
Anupādāno, devānaminda, bhikkhu parinibbāyati … pe ….
Because 'parinibbāyati' can occur in the here-&-now, I sense it is not inherently related to Parinibbānā (in the meaning of anupādisesāya nibbānadhātu).nibbāyati
ni + vā + ya
ceases to exist; becomes cool.
Therefore, in the stock definition of a Non-Returner, I sense the term "parinibbāyino" may not refer to the final attainment of here-&-now Nibbana (upādisesāya nibbānadhātu) or Parinibbānā (anupādisesāya nibbānadhātu).
AN 10.64 is an interesting sutta. It appears to say stream-enterers, once-returners and Arahant complete their respective paths "here" ("idha"). Where as non-returners complete their path (but not the path of Arahantship) "abandoning (vihāya") here (idha)". About five non-returners, AN 10.64 says:
"Parinibbāyi" is used in each five situations above. My sense is it does not refer to final Nibbana because AN 10.64 says the Arahant Path is finished "here" ("idha").Which five conclude their path after leaving this realm behind?
Katamesaṃ pañcannaṃ idha vihāya niṭṭhā?
The one who is extinguished between one life and the next [in the interval; while travelling], the one who is extinguished upon landing, the one who is extinguished without extra effort, the one who is extinguished with extra effort, and the one who heads upstream, going to the Akaniṭṭha realm.
Antarāparinibbāyissa, upahaccaparinibbāyissa, asaṅkhāraparinibbāyissa, sasaṅkhāraparinibbāyissa, uddhaṃsotassa akaniṭṭhagāmino—
OK. I will stop writing for now. However, I sense the "parinibbāyi" of a Non-Returner does not refer to Nibbana but refers to some lesser type of "cooling"; such as the purity of the 4th jhana or an immaterial realm.