Under safe for dogs you have water and dry area before letting them on it. Under cats you have wait until dust settles. Why?

Hi - Depending on the question, for example if the product doesn't require water, you would wait for the dust to settle for any pets/small children. If watering in is required, you would wait until the application dries to let any people/pets back into the area. There is no difference based on the pet just the product. Thank you.