I agree with most of what the author is saying, but the slogan that "a sufficiently detailed spec is code" can be misunderstood as "a sufficiently detailed spec is a program". The statement is only true if you read "code" as "statement in a formal language". Here's a (sketch of a) specification for a compiler:

> For every specification satisfied by the input program, the output program satisfies the same specification.

This is not a program and it does not become a program once you fill in the holes. Making the statement precise clearly requires a formal language, but that language can work at a higher level of abstraction than a programming language. So yes, a specification can absolutely be simpler than a program that implements it.