To compile a short treatment, the photographer does not have to involve third-party specialists, he can easily cope with this task himself. Moreover, it will add value to the photographer, saying that he takes his work seriously, and not just sends a moodboard with a text description of the shoot.
Remember that when choosing a photographer, the client also looks at the portfolio. If you are just starting out, it makes sense to take 2-3 shoots for free, but at the same time get a shoot in the client's portfolio and editorial.