A complex and difficult question. First, the term 'parinibbana', the Buddhist Dictionary by Nyanatiloka says:
"Parinibbana : 'full nibbana', is a synonym for nibbana; this term, therefore, does not refer exclusively to the extinction of the 5 groups of existence at the death of the Holy One, though often applied to it. Cf. nibbana."
I agree that 'parinibbana' seems to be used sometimes to refer to enlightenment attained in this life. I disagree with the rest of the definition.
If you are asking what happens after the literal death of a tathagata or arahant, the teachings do not say anything (except that 'he' is not reborn?).
The passage that you quote from Ud 8.3 may be describing a stage of enlightenment which is attained in this life. If so, then one would still be conscious.
The problem is made more complicated by the difficulty of defining what, exactly, is meant by the 'five aggregates' ( I believe that they can cease before death).
It is even possible that many passages which appear to be describing someones death are in fact describing a higher stage of enlightenment. Idiomatic expressions are frequently used - 'he makes an end', or 'he uses the knife' (a symbol of wisdom).
Even the word 'death' does not have to be taken only in a literal sense.
It is doubtful whether 'vinnana' really means consciousness - perhaps it means a certain kind of knowing. A knowing in terms of self?
My ideas are controversial and outside mainstream thinking, I would not wish to mislead beginners, you must start with the commonly accepted view.
Best wishes, Vincent.