This is a super interesting result. As others have pointed out, two sided die have been tried in the past but it was expensive and the backside components could

This is a super interesting result. As others have pointed out, two sided die have been tried in the past but it was expensive and the backside components could not be very interesting because you are limited in what you can do (for example ion implantation can shoot through the place you're trying to hit and damage the component on the 'other' side, not a problem when you are laying down the first set of devices on raw silicon, a big problem if you've got structures underneath you need to protect). Whereas just doing power delivery on the back side is much simpler proposition and you could likely make simple transistors to give you the ability to switch more fine grained power domains on and off for even better power and heat management.