Wuthrich writes "the presentist maintains that the sum total of existence can be understood as consisting of a three-dimensional manifold of spatially distinct but temporally equally present, and thus simultaneous, events or objects."
That's wrong: it's possible to have a model in which each ontologically existing thing experiences an ontologically independent temporal flow, while simultaneously keeping other temporal correlations. The upshot is there is no single notion of present at which everything obtains in the same R3 space. For two particles, a state is not given in the manifold {t}crossR3, where {t} is the set of all times of a given reference frame. A state is given by two points on ({tparticle1}crossR3)cross({tparticle2}crossR3).
Consider an astronaut that accelerates away from the earth, goes to Alpha Centaui, turns around, comes back, and stops. Because of the astronaut's acceleration, when we compare clocks the astronaut's clock will show a smaller difference in leaving-to-returning duration than our clocks on earth. (Of course, this assumes the astronaut makes the trip in a frame that accelerates a lot compared to the earth's acceleration around the sun et. al.). Nevertheless, throughout the entire journey the astronaut observed, of himself, that clocks in his reference frame evolve at a rate of 1 second per qualitative second.
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