Spicerack
You say the the FDA have 'sanctioned the use of 31,000,000 doses in the US'.
I've been to their website, and I'm not seeing what you're seeing.
The FDA states:
//Hydroxychloroquine and chloroquine are FDA-approved to treat or prevent malaria. Hydroxychloroquine is also FDA-approved to treat autoimmune conditions such as chronic discoid lupus erythematosus, systemic lupus erythematosus in adults, and rheumatoid arthritis.//
//The EUA was based upon limited evidence that the medicines may provide benefit, and for this reason, we authorized their use only in hospitalized patients under careful heart monitoring.//
//FDA cautions against use of hydroxychloroquine or chloroquine for COVID-19 outside of the hospital setting or a clinical trial due to risk of heart rhythm problems//
Is it possible that you're sources may have been referring to prescriptions for other ailments?
https://www.fda.gov/drugs/drug-safety-and-availability/fda-cautions-against-use-hydroxychloroquine-or-chloroquine-covid-19-outside-hospital-setting-or