You've found the photographer of your dreams and you're ready to book him or her.
ABC Photography* may substitute another photographer to take the photographs in the event of Bob's* illness or of scheduling conflicts. In the event of such substitution, ABC Photography* warrants that the photographer taking the photographs shall be a competent professional.
This photographer is letting the clients know that if a 'scheduling conflict' comes up, that another photographer can be assigned to the couple. This does not sit well with me for many reasons. One being, that if Bob finds another client that is willing to pay more for that date, he can choose another photographer for my client's wedding. Perhaps this isn't what Bob has planned, but the contract item is so vague, that Bob can in fact choose which wedding to shoot at will. He can even send substitute photographers to more than one wedding. Bob explains that he will send a competent professional, but isn't that a subjective term? Sure, a photographer may be on time and able to shoot photos, but didn't you hire Bob for his creativity and artistry? What if the substitute Bob sends does not have the creative eye you are looking for?
How would you feel if the photographer you hired wasn't at your wedding?