Is a puppy under 6 months who is not yet spayed considered 'unfixed'?

Many sitters only sit for fixed dogs and puppies but I feel as though there are many sitters who will sit for a younger puppy who is not yet spayed but under the 6 month age where they may go into a heat cycle?

On Rover, is it appropriate to mark them as fixed in the info and communicate that directly with the potential sitter rather than have them be out of consideration from the beginning?