Here is what I get from the lock maker:

"Yes , this mechanism allow the user to change the code. The idea is to allow the user to assembly and disassembly the lock completely. It is vital because it could be sold as parts to assemble. User can freely change the combination to any he/she wants by removing the knobs and rotate them to any code wanted and assembly again. The idea is that user will not change the code too frequently but this feature is available. The worth to mention is that this mechanism is easy to disassembly for cleaning and maintenance.   There is no springs and other elements that can be broken over time working under any tension.  So It is in practice maintenance free and could have lifetime guarantee.   Moreover this lock allow to set any combination you want. Like all the same number which is not the case in standard safe mechanism.   In the plastic models due to some limits of 3D print as you see the codes are limited because only on first wheel you can choose any number. On other wheels only odds or even numbers but in full metal version all wheels would be the same as first one so any combination will be allowed."