Is it required to size a generator for the fire pump locked rotor amperage (plus connected equipment) when the generator serves as a On-Site Standby Generator and the primary reliable source of power is through the Electrical Utility Service Connection? (Quotes taken from NEC 695.3)

There is a debate in my office whether or not the generator can be downsized to serve below the locked rotor amperage of the fire pump due to the manual trip switch (unsure if mandatory according to NFPA 20) on the fire pump controller. When the manual trip switch is activated, the fire pump is in a stopped state, and the generator is supplying the alternate power, the FLA would be placed on the generator.

So it is either acceptable to not be able to start the fire pump in the manner intended with the downsized generator or quite a bit of spare capacity is needed for an event that seems unlikely to occur (but could be quite catastrophic).