The basic core idea around this is that a person who dies goes to Sheol/Hades not hell where they suffer according to what they had done. Then at some point they get one last chance to repent before the great judgement where lack of repentance does mean being thrown into the lake of fire/Hell. Link where I read this theology from: http://www2.biglobe.ne.jp/~remnant/hades.htm
Let me start off by saying right now I have no firm position for or against this. I did have a strong position against the idea a person who died in this life without Christ had any chance of avoiding the lake of fire. And even debated a Jehovah Witness on the subject of hell and how it's different from Sheol (the grave) because they insisted no human beings go to hell.
Before going on I must be transparent. Hell bother's me a whole lot. It's not a joke to me. I've had nightmares about going there. If you want to see me actually cry talk about souls going to hell and getting tormented for endless trillions of years. My judgement is no doubt clouded by a desire for mercy and hope that a new chance to make the right choice exist.
In Matthew 12:30-32 the bible speaks of not being forgiven in this age or the one to come if you commit this sin. What if the reason it's worded this way is because people normally do get a second chance to repent of their sins after the first death?
I also do feel kind of skeptical because this theology sounds too good to be true. It would make explaining the gospel much easier for me and take away the atheist talking point about how God sends billions of people to hell just because they never heard of Jesus. It's just in my own experience things worthwhile are hard and aren't merciful to failure. I'm not going to say more than that as it's not my intent to attack what other's believe and hopefully those wiser than I know if this theology is mistaken or not.