Note the presence of the word pain. So, dukkha. Not the clinging, grasping forms of dukkha, true, but painful sensations are a form of dukkha since the khandhas are still present in a living arahant.
SN21.2 I believe refers to the arising of sorrow, lamentation, etc. from the standpoint of Sariputta’s mind being free of all greed, anger, ignorance, and clinging, so no dukkha or distress in terms of reactivity in the mind or afflictive mental states. But I’m in no position to take a firm stand on Sariputta’s realization.
And from SN22.86: Dukkhameva uppajjamānaṁ uppajjati, dukkhaṁ nirujjhamānaṁ nirujjhatī
What arises is only suffering arising, what ceases is only suffering ceasing.
This is how right view is defined. Ettāvatā kho, kaccāna, sammādiṭṭhi hoti.
Since all conditions are suffering (sabbe sankhāra dukkha) and SN56.11 “In brief, the five grasping aggregates are suffering” (pañcupādānakkhandhā dukkhā), and only the cessation/extinguishment of all this is the ending of all dukkha, how can the presence of the khandas while an arahant is still alive be utterly free of all dukkha, such as physical pain?
In fact, the presence of the khandhas themselves are a form of dukkha in the living arahant because “What arises is only suffering arising, what ceases is only suffering ceasing.”
Although there is no reacting with the “additional” dukkha of grasping, aversion, or other forms of reactivity, physical pain is a form of dukkha – even if it’s not experienced as me or mine by the arahant, because pain is conditional and final nibbāna is of course without conditions.
With respect and all best