Postils are by definition Bible commentaries or sermons not monographs

MJ. Smith

postil in British English

(ˈpɒstɪl)noun

1. a commentary or marginal note, as in a Bible

2. a homily or collection of homiliesverbWord forms: -tils, -tiling, -tiled or -tils, -tilling, -tilled

3.  obsoleteto annotate (a biblical passage)

Collins English Dictionary. Copyright © HarperCollins Publishers

Word originC15 (postille): from Old French postille from Medieval Latin postilla, perhaps from post illa (verba textus), after these words in the text, often the opening phrase of such an annotation

The three books which form a series which includes Rollefson, John. Postils for Preaching: Commentaries on the Revised Common Lectionary, Year a. Eugene, Oregon: Resource Publications, 2016. are the primary offenders being erroneously given the resource type of monograph. I own a number of Text Creation Partnership documents with the same problem but I'm uncertain what tagging I should expect on them. If you filter the library by postil and sort by type you should catch all the errors not just those in my library.