I think when you design a new device from the ground up you make them fit in a way that allows the remaining space to be a single large rectangle to be entirely

I think when you design a new device from the ground up you make them fit in a way that allows the remaining space to be a single large rectangle to be entirely filled with battery. This might require custom PCB to have some L shapes. Instead it looks like they took pre-existing components from other devices such as Pixel phones or the Google Home and put them in a larger case.