It's true - I have recommended a 30-day refill to all my new owners. Your skin empties it's pores much more completely into a hot tub than any shower, add to that the learning curve of over attention, extra visitors, laundry soap, and general extra use a tub gets while brand new - AND throw in the wet-test from the factory, and you will be pleasantly surprised by how good the water feels and acts after this one-time water change.
Bill will not have the normal oil ring because he went right from his Dynasty to his shiny new spa, but most new owners don't currently have a tub and most are amazed at the water line which forms the first few days...