c) Why Boeing is not using this feature in flight on the EDPs (used by Boeing in the IDG or VFSG, and even the CSD) ? I wrote "in flight" because Boeing (not Douglas) uses only one EDP per engine and there is no benefit for this feature on the ground for the dispatch.
Boeing doesn't use a clutch, it uses a servo valve to 'depressurize' the EDP such that the EDP isn't involved in the associated hydraulic system and is basically just free-wheeling.