This will allow for additional access to the aft of the vehicle, following what is understood to be positive results from initial inspections conducted while the vehicle was sat on the landing pad.
As for SN15, numerous options remain open to SpaceX, from reflying the Starship to conducting ground tests including cryotesting the vehicle in what is a post-flight configuration or even Static Fire testing if the option of another flight is removed.
Reflying SN15 would be an attractive option to SpaceX, a milestone that caters towards the company’s reusability mantra. It would also allow for additional flight data that could be incorporated into the potential flight of SN16.