But it also says that:
Read carefully. The scene is ... wait for it ... IN HEAVEN! Are you of a mind that purgatory is in Heaven? God forbid such error!
“The building allegorizes the man on the day he is judged”
No, it does not. The “building” is the church, which the “builder” has been working on. What Paul says is “If anyone builds on this foundation [Jesus Christ] using gold, silver, costly stones, wood, hay or straw, 13 their work will be shown for what it is, because the Day will bring it to light.”
The quality of the work the man did in building the church “will be shown for what it is” - not literally burned, since it is just a word picture. It will be revealed, or ‘made manifest’ - exposed.
“of what sort it is (hopoion estin), qualitative relative pronoun”
It is not “judged” or condemned, and certainly is not an “imperfectly purified” soul being made better.
All is in the context of workers, laboring under God, on the church - and the illustration shows why Paul says “He who plants and he who waters are one, and each will receive his wages according to his labor...Let each one take care how he builds upon it.”
“It” is the church, not the individual’s soul.
Very clear, except to those who do not want it to be clear.