None of it is solely human generated. The P&C is human augmented as OceanWx has said plenty of times...they can raise or lower the temps, sky, POPS, QPF etc but it's still getting spit out as a gridpoint.
The Zone Forecast isn't entirely human generated either... no one is sitting there typing that out for each and every zone for every 12 hours. The zone forecast averages the grid points in the zone and smooths it out to make it easier to digest.
Like a wind speed of 8mph in the grids might yield a P&C of 7-11mph, while the Zone interprets it as 5-10mph.
But like I know in my zone, it's averaging temperatures from high elevations and the valley because my County has huge terrain changes. The mean ends up having high temps a bit lower than what I see, and lows are a bit warmer (i.e. the mean of Valley and mountains has a lower diurnal change than the valley sees).
All of the forecasts have human input but none of them are solely just a forecaster sitting there typing it out for every county in their area.