Tobias wrote: “Thus Nibbana is not another realm.”
Exactly. One is either in this world of 31 realms OR has attained Parinibbana.
– A living Arahant is still in this world. After his/her death he/she will LEAVE this world of 31 realms and merge with Nibbana. That is what is meant by “Parinibbana” or “full Nibbana.’