According to Brownstone’s planning application for 12 Mint Plz https://sfplanninggis.org/pim/?tab=Planning+Applications&sea..., the proposed use is Residential (which is Principally Permitted) rather than Hotel (which requires Conditional Use Authorization from the Planning Commission), and also I do not see an Intermediate Length Occupancy application (which would be Principally Permitted), so they are only permitted to offer year-long leases at this time.