My understanding is that on 3-class service flights an upgrade list contains both passengers requesting upgrade form Biz to First and from Econ to Biz. Once from Biz to First upgrade was processed and still seats left in First likely means all remaining passengers on upgrade list were from Econ to Biz upgrade passengers.
My understanding is that AA does not do double upgrade. Which means got upgrade from Econ to Biz using 500 miles certs or EXP/PLAT-PRO complimentary upgrade then asking to use miles to upgrade from Biz to First. This don’t happen.
Also, seems you indicated from Biz to First upgrade was processed first, then standby passengers were processed into First. Do you know this for the fact? I thought if there was F fare passengers trying to standby on a flight, that standby passengers are processed before upgrade passengers.