It depends how and how quick you're drying these films but you're right about the "problem" . The 120 roll film versions are made a different polyester PET base which gives more curl. The 35mm is certainly not any problem at all about the curl problem.Problem with those types of film is curling.
Advanced (and more expensive) films have a non-curling layer on the back side. Then the PET layer is much more flat. Most Rollei films are equipped with this technique. The only exception are the Rollei Retro films which are based on tri-acetate (Agfa APX) layer.