I don’t understand your post. If only the top most sinful people are tortured then why is Gehinnim full of pain and punishment? It should only be partly full of pain and punishment if it’s only in the top tie?
And why is cleansing of the soul in gehenim a fabrication? I would assume, without basing my thoughts/feelings on sources but what on what I’ve been taught, that punishment in gehenim is individual. Some people need cleansing of sin and are afterwards get into gan Eden while some mass murderers like Hitler y”s and Stalin y”s are there forever.