This seems to be a common expression in AE course descriptions, e.g.
All students must take 12 hours of humanities, 9 hours of social science/history, 7 hours of natural sciences/mathematics, 6 hours of religious studies/philosophy and interdisciplinary studies, 3 hours of ethics, 9 hours of electives from the liberal arts and sciences or interdisciplinary studies, and a capstone synthesis reflection.
A capstone (definition 2 in WR dictionary) is a final touch; a crowning achievement; a culmination
So it looks to me as though your supposition is correct. It's a piece from each student at the end of their course, outlining their impressions of the course and its impact on them.
Remember I don't know about American universities; the AE speakers should come online here in a few hours time.