Not understanding the point you're making - presumably you agree that heaven and hell would be meaningless and would not work as a method of control or influence unless people relate them to real-world experiences?
I think the key point is that people believe they exist - that's what allows them to work as a method of control or influence.
If you can't imagine it, it can't affect you. People need to relate to a concept for it to generate feelings that influence their behaviour.
But surely the whole point it that they go beyond what it imaginable - so, sure you have experienced good stuff in the real world - but heaven is meant to be unimaginably better, unimaginably good. Sure you have experienced bad stuff in the real world - but hell is meant to be unimaginably worse, unimaginably bad.
But the other element which is challenging for people to imagine is the time scale - this unimaginably good stuff or unimaginably bad stuff goes on for ever, to infinity. And for ever/infinity is also something which people struggle to imagine.
So although there is a hook into the imaginable - people can imagine good/bad stuff that goes on for a long time, heaven and hell take that to a new, basically unimaginable level.
But I come back to my first point - the key here is
believing that you are going to have unimaginably good/bad stuff for ever. That's what works in terms of control. If you believe it then it would also work if it were really, really good/bad for a really, really long time (but not for ever). It doesn't work if people don't believe heave and hell actually exist.
But the other point that goes along with
believing is that no-one can verify this for you - no-one can come along as say 'hey, yes I was in heaven - wasn't really all that it was cracked up to be and they kicked me out after 6 months' or 'hey, yes I was in hell - wasn't really all that bad at all - all the fun people were there'. The point is the unknowable promise and the unknowable threat which is the key to the control as long as you believe in the promise and believe in the threat.