It’s not the clergy going through purgatory. The chapter is talking about whether the “people” of the church will last or will they be burned by the fires of trials. It’s the members of the church that will either be found to be wood, hay, stubble or gold, silver, precious stones. Those who the pastors only fed with the milk of the word will be the wood, hay and stubble. Those who are fed with the meat of the word will be the gold, silver, and precious stones. If the pastor fed with meat and made strong Christians who last through the fires of temptation the pastor will be rewarded. If the pastor fed with milk only and all the people they taught fall away he will still be saved but will receive a lesser reward.
Where is that in the passage? It speaks of "every man", not the pastors; it speaks of burning off stubble, not of "lesser rewards". Read what is written.