The problem arises especially in the keys alone.

For example look a UK layout keyboard, it's QWERTY, and a german one is QWERTZ. Take down "Y" and "Z" keys.

Simply they aren't the same shape. If you replace the german "Z" key into the "Y" position" of a UK layout keyboard and vice versa, you'll see a slight different in touching.

That applies in all keyboards I pressume.

EDIT: Am I way off topic in that?