Could you explain how citta is cognition ?
Are you equating citta with mano (base) or vinnana or all the same ?
There is no direct evidence in the sutta stated the SE attained nibbana . Having Knowledge of water ie nibbana not the same thing with Touching the water .One who knows and sees that these phenomena are this way is called a stream-enterer
Kosambi Sutta (SN 12.68)There is water,’ but he would not be able to make bodily contact with it.