Looks like it’s a cultural thing, since an explanation of a grammatical point concerning a dead language does not entail that the actual construct must actually exist. Does your academia read the proposition “So, when it says that “Stream Winners anupādāya”,” I can only use a real existent example, and not a hypothetical sentence? If one is trying to illustrate a grammatical point, it seems perfectly legitimate to posit a hypothetical.
Rather than split hairs over my intention, here are some very interesting findings about the suttas in SN 22 which use -
Vimuttattā ṭhitaṃ. Ṭhitattā santusitaṃ. Santusitattā na paritassati. Aparitassaṃ paccattaññeva parinibbāyati.
I’ve compared them to their SA parallels. As mentioned previously, the SA sutras do not have the above in the wisdom sutras. Instead, they use this other pericope in the wisdom sutras -
Being liberated, in the world there is no thing to which to cling and no thing to which to hold on. There being no thing to which to cling, or to which one is to hold on to, one realises extinguishment. One knows: ‘For me birth is finished. The Holy Life is established. Done is what had to be done.’ One knows: ‘I will not experience future becoming.’
SA 39, parallel to SN 22.54, transl Ven Analayo
Variants of this are found in eight SA sutras, based on the SC search engine, 5 of which are parallels to the suttas in SN 22 which you cited.
Needless to say, the above pericope comes close to the Pali -
So evaṃ amaññamāno na ca kiñci loke upādiyati. Anupādiyaṃ na paritassati. Aparitassaṃ paccattaññeva parinibbāyati. ‘Khīṇā jāti, vusitaṃ brahmacariyaṃ, kataṃ karaṇīyaṃ, nāparaṃ itthattāyā’ti pajānāti.
Since he does not conceive anything thus, he does not cling to anything in the world. Not clinging, he is not agitated. Being unagitated, he personally attains Nibbāna. He understands: ‘Destroyed is birth, the holy life has been lived, what had to be done has been done, there is no more for this state of being.’ : SN 35.30
The trope “na ca kiñci loke upādiyati” is also well-known from the satipaṭṭhāna texts.
It looks very suggestive that the Pali tradition may have picked out the wrong pericope to append to the SN 22 series, since the SA parallels to the SN 22 sutras, as well as the SN 35.30/31 wisdom texts use the other pericope about “not clinging to anything in the world” to lay out the causal sequence leading to non-agitation.
I wonder why Bhikkhu Bodhi treats the silent hoti in “vimuttattā ṭhito” as implying “it is”. Elsewhere, ṭhito comes out very clearly as a reference not to a meditation but to a jhana-attainer. Eg -
Here, householder, quite secluded from sensual pleasures, secluded from unwholesome states, a bhikkhu enters upon and abides in the first jhāna, which is accompanied by applied and sustained thought, with rapture and pleasure born of seclusion. He considers this and understands it thus: ‘This first jhāna is conditioned and volitionally produced. But whatever is conditioned and volitionally produced is impermanent, subject to cessation.’ If he is steady (ṭhito) in that, he attains the destruction of the taints. : MN 52
See similar passage in MN 64, AN 11.16, and AN 9.36. In all of this cases, it is the meditator who is ṭhito.
Likewise, with the exception of the SN 22 suttas, the other instances of contentment largely refer to persons, rather than the nuts-&-bolts making up the experiental entity.