Here is a photo from one of my dissections of a main-line shoe:
You can see the surface texture of the layer under the one I peeled back, and it has a finely patterned appearance as if it was stamped out. Whatever it is... leather, paper, some other unidentified fiber, it isn't stacked leather.
I have no idea how long they've been using this material, so this may not be a revelation. Even in a lot of the high end English shoes, pre-assembled heels are the norm. But, the better ones are still leather.
I certainly get outspoken about certain components being made of inferior materials, but I will say that synthetic heel and toe stiffeners are also the norm. There are a few out there that use leather in the non-bespoke world, but not many. So, AE isn't really violating any GY-welted shoe manufacturing standards there.
Frankly, I'm much more worried about how many models are shifting to Poron insoles than I am about the synthetic heel stack since the heel stack gets replaced at recrafting no matter what. The insole, however, is there for life.
Shall we get DFW in here to talk about quality of manufacturing etc? Goodyear welting itself means you are cutting a corner. You're replacing the work of a skilled shoemaker to sew the welt on by a cheap laborer that uses a machine to sew on the welt. This is one of the inventions that made shoes cheaper and more affordable for the average joe but its cutting corners just like replacing leather soles or heels with cheaper materials (and arguably sometimes that actually also makes them better - commando soles for Montreal winters vs a nice leather sole anyone?).
So the real question I think is whether you're honest about your process. Does AE say they use leather heels? Probably not but they probably also don't stick your nose in the fact that they aren't since people will believe what they want to, if you don't. I.e. they want to believe that goodyear welted shoes are "handmade" (just ask DFW or any real shoemaker about that) and they want to believe that their chosen shoe's heels are all leather. It's much easier to make fun of the people that pay full retail for say a Cole Haan and talk about people that don't know cheap corrected grain leather from good leather than to accept that you yourself didn't even notice that your favourite pair might not actually have leather heels