John, I don't know anyone who treats " ... a sequence of events like days as causal ..." I don't even understand what that could mean. Julian Barbour's view simply rests on what Einstein coined as "Mach's principle," meaning that every particle in the universe moves relative to every other particle. The critical difference between Mach's principle and general relativity is that GR disallows any causal connection between bodies that propagates faster than the speed of light ("All physics is local."). Local causality isn't a feature of pure relativity; i.e., Mach's mechanics.
"There is no more a 'fabric of spacetime' anymore than there are giant cosmic gearwheels causing epicycles."
Epicycles are caused by mathematics, not by anything physical. Spacetime is demonstrably physical. Be scandalized by the facts, if you must. However, if one speaks of changes in relations among mass points, one speaks of changes in relative points of spacetime. "Matter tells space how to bend; space tells matter how to move" (~ Wheeler). That doesn't settle the question of whether time is fundamental or whether space is fundamental -- it does, however, settle the question of whether spacetime geometry is fundamental. It is. And it does settle the question of whether information is fundamental. It is.
The remaining question is how continuous spacetime geometry relates to discrete quantum information.
Tom