Welz and Kralik - Design concepts

I recently implied that a Kralik piece was a copy of a Welz piece and got told-off - "Ive been collecting for twenty years and this is definitely Kralik" this person said. It WAS a Kralik piece but I was astounded at the direct copy-cat design work, here ther is a oroduction method similarity. Here you can see Kralik and Welz producing two vases then continuing the forming to make fan shapes. I have noticed this before in tango; some examples were made with an applied rim and some without any rim...or large bowls made with an applied base and the same bowl made without an applied base. I guess its like the saying goes "Art is knowing when to stop" .