Each landscape designer is unique. Perhaps it’s helpful to compare them to artists.
Some landscape designers work to develop a unique style, then tend to design in that style until they are ready to move on to something new. You could compare these designers to artists like Picasso, Brach, Miro, Klee, Rodin, Henry Moore, Monet, Norman Rockwell or Toulouse-Lautrec. Their work done during a certain period is easily recognizable.
Others are more like illustrators, adapting their style to fit the project. Many great illustrators enjoy the challenge of working in different media and different styles to achieve set goals. Nonetheless, they do tend to favor certain styles and typically dislike copying other artists’ or illustrators’ work, preferring instead to create something original.
Hiring a landscape architect is similar to commissioning an artist. If you hire say, Picasso, you probably expect to get something resembling his other work, perhaps with some of your input concerning the size of the piece, the subject or the theme. If you’re hiring an illustrator, you were probably impressed with his or her work, have looked at examples in a portfolio, and have an idea of what style you’d like for your oeuvre d’art.
This is why it’s a very good idea to look at a designer’s body of work, then talk to them about what you’d like to accomplish. Just because they never built a certain type of design does not mean they are not interested in taking things in a new direction. They may even have proposed something similar as a concept, but that project took a different direction.