IMO, it is somewhat disingenuous of Geezer to make a statement of this sort without defining what the (alleged) problems used to be. In the environment of Seventies Black Sabbath, I would guess note definition and outright volume versus the guitar rig of Tony Iommi.
For what it is worth, Mr. Butler seems to be getting his signature on quite a few brands at the moment. JHS/Vintage has a Geezer bass. There is the EMG pickup under discussion here. All that is missing is a Fender sig P Bass. (This would explain his reluctance to roundly slag them off.)