Hamilton standard props go to the finest pitch available when no oil pressure is present.
The reason for this is..... if the prop governor system experiences a loss of oil pressure......but your engine still has oil pressure, you still have a setting that generates thrust instead of beating the air with feathered blades.
Aeroproducts props have thier own oil system separate from the engine and possibly an accumulator that will allow feathering after an engine failure but you had better be quick with it.
Curtis electric props are electric and will hold the position they were last set if you lose power.