My understanding is that the sheer size of Tesla's battery pack is too large to take a layered approach - at least across the whole size. That forces the desig

My understanding is that the sheer size of Tesla's battery pack is too large to take a layered approach - at least across the whole size. That forces the designers to go with a segmented approach, in which case the cylindrical is tried and true. From a safety perspective, it also has many more years of data/research behind it. It would be more tolerant to defects. Trying to create small sheets that are then rolled up is easier than creating big sheets, just like smaller silicon processors have better production rates than ones of equal complexity but larger surface area.