[dajonker]

Perhaps it's a matter of rule-based versus principle-based view of the world. Generally speaking, in a principle-based system, there is room for different interpretations of the stated principles. Edge cases usually don't require special mention. In a rule-based system, rules are strictly defined and enforced with little room for interpretation. Anything not explicitly mentioned is a grey area and edge cases often end up amending the rules so they are covered as well.

Sounds to me like the author prefers the rule-based approach and/or is assuming these rules are strictly enforced.