JeffTilley How I read it is two-fold:
"Hydroxychloroquine and chloroquine have not been shown to be safe and effective for treating or preventing COVID-19"
and
"A summary of the FDA review of safety issues issues with the use of hydroxychloroquine and chloroquine to treat hospitalized patients with COVID-19 is now available. This includes reports of serious heart rhythm problems and other safety issues, including blood and lymph system disorders, kidney injuries, and liver problems and failure."
So there seems to be no correlated benefit but additional health risks.