The German knife is simpler in that there is a single obvious way to grasp the knife.

Edited to add: I still have no idea how that makes it less "Japanese" than the Japanese knife.

I would summarize it as:

     German design goal: functionality and comfort, user is at the center.

     Japanese design goal: aesthetics, the tool is at the center.

It is possible, that a Japanese chef will feel and work better working with an aesthetic and clean looking knife. The chef's skill is praised in as much as it can make use of the beautifully designed knife (i.e. the craftsmanship culture).

A German (Western) chef will work better with any knife that fits his hand better. The chef is at the center of the design. A knife is an extension of a chef's hand.

I think the Japanese knife is at one pole of the fundamental user interface dilemma: to what extent do you cater to common actions at the expense of expert actions? The Japanese knife says that any concession made to one specific use will unacceptably hinder other uses.

The German knife is specialized for one particular hand position. In a way, it is actually prescriptive and restrictive: if you try to use it a different way than expected, you will have an inferior experience. The designers (hopefully) studied usage and decided that they could optimize for the common case without hindering other cases too much, thereby getting a better result. It doesn't matter if uncommon cases are a little awkward.

It's just common sense that the optimum design will reject the do-nothing approach and provide some kind of non-use-agnostic tweak. However, ten years of software development work have given me much more appreciation for the assumption embodied in the Japanese knife. It's pessimistic and will never be the best (except in the eyes of design gurus who never actually use stuff) but by god it will never stop you from doing what you want.