Brother I'm sorry but I'm not sure if I'm understanding your point. I don't believe that means they were exonerated....even if God wasn't imputing their personal sins to them before the Law (if that is the right way to understand that verse), the rest of the passage indicates they were still under condemnation by inheritance....because of Adam's sin.
Romans 5:12-14 KJV
12) Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned:
13) (For until the law sin was in the world:
but sin is not imputed when there is no law.
14) Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression, who is the figure of him that was to come.
It's pretty simple. Before God tells a man to do and not do, though the man doesn't do what he ought, and does do what he ought not, God doesn't count it against him because God hadn't yet told him so.
The man still dies, because sin brings death, so they died. But wihout the imputation of sin against them.
Now, is all we need to be forgiven of sin and we can live with God? No. God doesn't have dead men in His kingdom, and so we must be born again.
So when you consider Jesus preaching to the spirits in prison, who were disobedient in the days of Noah, perhaps it was to announce Christ's victory, and to let them know He's rescued them all, and they can be alive again and live with Him.
This isn't me. This is the passage. I'm just telling you what it says. Before the Law, sin was not imputed. And it may not have been imputed to others who had no law. I can't say how far this extends.
This is one of the best chapters of the Bible to study as deeply as one can. Romans 4-8. These are key chapters to know through and through, inside and out.
Much love!
