I found this article gives some context:

"The authors used a cancerous liver cell line. This is important for two reasons; both of which were acknowledged by the authors. First, cancerous cell lines replicate, whereas our liver cells typically are not replicating. As such, even if DNA representing the viral RNA was integrated into the cell, no other cells with the altered DNA would be produced." source: https://www.chop.edu/news/feature-article-no-study-does-not-...