It's a good example of how you can overengineer a relatively simple format.

The reason is that they specify a boolean value as either "true/false" or "yes/no".

The last alternative causes problems not only for the Norwegian country code (no), but also in cases where you need to specify the actual word "yes"

You could of course end up with the same problem if you need to specify the literal "true" and "false", but by overengineering the acceptable boolean values, they increase the potential problem areas.