I'll try to make it clearer for you.
This is what you said.
"What I am questioning here is the purpose and the practicality of having an unenforceable rule."
Based on that logic...
There's no reason to have a rule/policy against a race changing the start or finish description on a certification map and displaying that changed certification map on their race website, because there is no way to enforce that rule either.
There's no reason to have a rule/policy against saying your race uses a USATF certified course when it doesn't, because there is no way to enforce that rule either.