Here's another thought: I doubt AA intends for it to stack. So even if (because of how it's coded) it does intiially stack, as soon as that comes to AA's attentiion they'll try to end it. (And I suspect they'd have an easier time ending something like that than they had with ending "all miles from all sources" counting toward MM status.)
So let me revise what I wrote above: It's extremely unlkiely to stack in the long run, but whether it stacks for a short time (and they don't "claw it back") is a little harder to be sure about.