Hi David,
You are correct, the JSON data labeled “pm2.5_aqi” is adjusted to provide a US EPA AQI value. It is important to note that the non-converted values are also available as JSON data. Those would be the atm or cf_1 values.
You may be interested in reading What is the Difference Between CF=1, ATM, and ALT?.
Lastly, I don’t think we have this information expressly noted anywhere, we can look into doing that.