Aluminum is harder to weld (takes more skill and different equipment) that steel, and it works differently from steel when trying to re-form it (i.e. bang out the dents). Plus, I'm not sure how the aluminum alloy is with respect to body fillers, but I'd think they'd have them figured out by now.
It's basically no different from aircraft aluminum, and repairs have been being made to aircraft with aluminum skins for decades, so the knowledge is out there, but maybe the proper equipment just hasn't made it to automotive repair shops yet.
Most filler in use in the industry doesn’t adhere well to aluminum panels, FYI. Basically, you have to retrain and get the proper equipment to properly repair aluminum panels - and get documentation on each car so you know where you can repair and where you have to replace.