I personally find this contradictory considering that he also seemed to subscribe to the block universe theory which implies substantivalism as opposed to relationism when he stated - "The distinction between the past, present and future is only a stubbornly persistent illusion." or am I missing something here.
Someone like Brian Greene for example in his book 'Fabric Of the Cosmos' makes it specifically clear that he regards space-time as a physical entity and not a mathematical abstraction which I guess would make him a substantivalist, in a recent documentary he expressed his belief that Gravity Probe B which measured an effect on space-time curvature provided evidence to support this view, how plausible is this claim?