I can see the argument from a certain perspective of the language, outside of context.
But remember when this amendment was passed. Right after the Civil War.
So, they wanted an amendment to bar traitors from federal office. Then they put in a section saying Congress has to actually make laws enforcing that rule, or it does nothing. And then, they didn't make any such laws?!
So, what, they went through all the work to make a constitutional amendment, and then it does nothing?
No, they clearly felt that the rule was clear enough as it was, and section 5 is there to allow Congress to make supporting laws built upon that to help enforce that rule. But that rule should have teeth on its own.