If I have a confirmed Business/First award ticket and I standby for a earlier flight that day what priority does standby come in versus all the upgrade requests / instruments

Is it just as if I've waitlisted for the award fare class to open up on the target flight

I just did a standby on an America First Class transcon and it worked fine, got the target flight I wanted despite no award F seats opening up on the target flight. Although I think the upgrade list for these seats is very thin, since top tier AA people have to burn the equivalent of a GPU to go from buinesss to first on the 3 cabin transcon and since business is already a flatbed there isn't huge demand