Does a Copywriter Need to Be an Expert on the Subject They Are Writing About?

On a freelancers website, I recently noticed that clients were hiring writers who described themselves as being experts in a particular field. So for example, an owner of a landscape gardening business, chose a writer who stated that they specialize in the environment and biology. There was however, very little mention of the writer's knowledge and experience of digital content. Should in that case copywriters emphasize that they are experts in a given subject or present themselves as versatile, all -rounders, who can adapt their writing style to any topic? I personally think the latter, especially when it comes to writing B2C content. Why? Because, the copywriter will be looking at the company's products and services from the same angle as potential clients and will be using words that will be familiar and relevant to that particular target group.
As a business owner, you will be hiring a copywriter to market and sell your products not to write a white paper on them.
A copywriter who can write content that is,

• scannable
• optimised
• usable
• enticing

can take on most projects, without having a degree in the subject. Writing about a new topic is always a challenge and a welcome
change especially if the copywriter is hired to write about the same industry just because they are familiar with it.
No two companies are the same, even if they operate in the same industry. Each has it's own particular brand image, tone of voice and their own clients and customers. Our expert knowledge of a particular industry, cannot make us assume that content that is effective on one company website would be as equally effective on another. When faced with a new project, the copywriter needs to do their due diligence which includes finding out as much as they can about the company, the unique selling points of the products and services and their online competitors. If we just rely on our knowledge of particular subject or industry, we might as well let the business owner write their content as they will know as much if not more then we do. In most cases our clients will not be digital gurus which is why they have sought our help in the first place.
It is the job of the copywriter to think about how the client's customers will interact with the content, how best to facilitate their user journeys whilst they are on the site, and most importantly encourage them to take action.