Quote by JDoolin
If there are a finite number of clocks then the central clock is not arbitrary. If you have an infinite number of clocks, then the central clock is arbitrary.

I don't see how the number of clocks makes a difference. In the ballistic explosion the central nonmoving clock is at the heart of the event, experiencing no velocitybased time dilation giving it a unique quality that none of the others have. In the spatial expansion version, I acknowledge that no clock is unique and infact suggest that all the clocks are synchronised since none of them have an actual velocity.
In the first case I simply put forward that the central clock is actually central, nonmoving and not in a gravitational field making it an example of an otherwise hypothetical concept, that cannot be found so easily in our actual universe. But then, I put the same thing forward for the second example, but this time say that
all the clocks are representative of the hypothetical coordinate clock.