That is THE worse advice EVER.
You want a developer that can take your pseudo spec (and I say pseudo because if they are detailed enough, then you should be able to code them, since you are hiring a developer you don't know the devil that will be hidden in the details), interact with you, and give you what you asked OR BETTER.
Non-technical people need the counterweight. This advice is like telling the doctor "I don't pay you to think and figure out what I have, just to write the prescriptions, and is much cheaper"