Keep in mind, the people of that day had no doubt there was a purification process after death. Why state the obvious? Allusions (which are throughout both the Old and New Testaments) make the point. Fifteen hundred years later, some began thinking that an automatic pass into heaven was given to all who believed in Jesus. No more need to worry about sins, past, present, or future--all taken care of, so no need for purification as some decided God only sees Christ's blood that covers all sin.
There are two ways of looking at these conclusions. The first is that they are not that logical. But the second way of looking at it, Is what great faith. These people have faith their sins don't matter at all if they believe Jesus removed all taint of all sins they would ever commit a couple of thousand years before they were even born and were committing those sins. Jesus put much stock in faith, not just great faith, but faith the size of a mustard seed. I wish all these people the best.
Keep in mind, the Bible tells a different story from the conclusion Luther and others leapt to. The Bible also asks for great faith--and the faith the size of a mustard seed. Faith is a strong connection between the two.