Finnish PET beverage bottles are typically very boring.  

It is one of these..
unfortunate missunderstandings that plastics can be formed in any shape. It is also the reason why so many plastic products have a shorter than normal lifetime...they are simply badly designed. But it is also a missunderstanding that shape is only the result of manufacturing. In the case of water bottles the transportation through filling machines, labeling, shrinkwrapping, stacking etc. has a bigger impact on the shape than the manufacturing process...