Past tense .
18¶For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit:
19By which also he WENT and preached unto the spirits in prison;
Jesus is not crucified, buried ect more than once.
That means Jesus died and then His living Spirit went to preach to those in prison before resurrecting. They were given the gospel and you can't have the complete gospel message without the crucifixion. Next Jesus resurrected.
In John 5:25-29 says the bad and the good, the dead and the living, will be resurrected and judged. So death, resurrection, then judgment? Then there is a delay between death and judgement. The important question here is where are these deceased people waiting before the resurrection?
This infers that there is a prison in the afterlife and that Jesus can go there, but it isn't identified as hell. However, that does not mean it isn't hell.
It does raise important questions about why someone would be given the gospel after judgement and sentenced to hell.
Therefore, it is logically inconsistent to say the spirits in prison are in hell. This only makes sense pre-judgement in the afterlife. This is where the idea of purgatory comes from.