Yes. You wouldn’t make a film without a screenplay.
Unless you’re Roberto Rossellini. (But he was a screenwriter first, so he actually used the camera as a pen.)
Your competitors are following a well-worn path to creating their next piece of media. They brief a design agency, push back on the initial quote, see some color mockups with lorem ipsum in place of copy, uhmm and ahhh for a while, tick off the mockup that is the least worst, look over a final draft of the copy, realize some important elements are missing, request multiple revisions while trying to avoid additional costs, then finally approve a version before the money runs out.