I can't answer the AA powder question, cuz I don't know.
From my 50 years of handloading conventional and a few wildcats calibers, I have usually found there to be some variation between various LOTS of powder from any given manufacturer. And, when comparing burn rate charts, there are examples of where the order between two adjacent powders flip-flops between any given chart.
So, point being some healthy skepticism is in order whenever two powders are said to be "identical", especially if they're from different manufactures.
Maybe it's just me, but I don't put much faith in "identical". If I run out, I'll give the "other one" a try, but will work it up like any other new powder and hope to be happily rewarded.
I've had my share of "surprises" over the years. But, I still have all my eyes and fingers, primarily due to NOT trusting the "identical" claim. When I find a powder that works, I buy a quantity that will last me for a while, powder from that same LOT #. But, anytime I have to change LOTS (not to mention a different powder), I back off ~ 10% and work back to accuracy (which may or may not be the same weight/volume as with the previous LOT).
I don't know if I added anything to the conversation that most of us didn't already know. But, I guess I would take the "identical" claim as simply a suggestion for another powder, and treat it like any new powder load development.
Bottom line? When I hear "identical", my eyes get squinty and my tongue pokes into the side of my cheek!