I have to question that. There is no linkage between the fuel distributor and the crankshaft; so the fuel distributor can't know if a cylinder is in its compression stroke. My understanding is that a CIS injector is open as long as there's sufficient fuel pressure, regardless of what the valves and piston are doing. That's my understanding of the basis of 'continuous.'
I believe, though I haven't tried, that one can swap lines between the fuel distributor and the cylinders with no negative effect. If this is true, then I raise the original question again, why not have a common rail?
The only thing I can think of is that there is some dynamic during the various engine cycles that individual fuel lines isolate.
Good point to clarify. I understand the metering function of the fuel distributor, just not why fuel is essentially distributed at the point of metering and not later. Why have six metering slots on a six cylinder engine if all six metering slots do the same thing at the same time?