You almost got to the point, TGS.
If Ven. Sariputta was in Nirodha Samapatti, he would not have any saññā.
– But he stated that he was still perceiving, meaning he still had saññā arising.
– If one still has saññā, that means one still has citta arising. Yet, he did not perceive anything in this world (na idhaloke idhalokasaññī) or anything of paraloka (na paraloke paralokasaññī)
– Ven. Saripuatta was in Arahant phala samadhi! There only pure, undefiled citta (pabhassara citta) would arise. A pabhassara citta has only seven uncontaminated, universal cetasika (with pure saññā and vedana). That means one is ONLY aware that one is alive but does not perceive anything in the world.
– A citta normally would contaminate in nine stages. Even for Arahants, it will go through the mano, manasan stages. See “Citta, Manō, Viññāna – Nine Stages of a Thought”
– In contrast, no citta (i.e., no saññā) in nirodha samapatti: “Nirōdha Samāpatti, Phala Samāpatti, Jhāna, and Jhāna Samāpatti“