It's pretty close actually. But the more useful and more general application of it would be to think of Time Error as a parallel time axis that
only time travellers move though. Ie: A 5D time axis that only time travellers experience by time travelling. This neatly explains why Crono and co. seem to exist on a time axis of their own by time travelling. In your example, not only do time travellers move through time error to Time Error X when Crono enters the gate, but so do all
normal people in the timeline as well. So if you were to think of Time Error this way, you would still need an extra 5D time axis to explain events in time.
So basically, whenever a time traveller actually time travels they make a 5D move through Time Error. So an entire timeline can be thought of existing at Time Error 0 without Marle in 600 AD. And then at Time Error 1 an entire timeline can be thought of existing
with Marle at 600 AD.
But what is interesting that Eske pointed out in this thread is that two time travellers who travel separately from each other on the same timeline end up at the same point in Time Error:
Time Error 0: Marle goes to 600 AD at Time X. Crono goes to 600 AD at time X+10 minutes.
Time Error 1: Marle arrives at 600 AD. Crono arrives at 600 AD ten minutes later.
So you see, here I have accounted for the discrepency in time between when they have entered the gate, and also for their 5D movement through time. Time Error was not necessary for the time discrepency, just for the 5D movement. This example also shows that the two time travellers don't end up at different points in Time Error, and that a future isn't sent to the DBT
every time someone time travels, which is a belief that the Compendium still holds.
Due to the nature of the Chronoverse, a potentiality is not automatically actualized. Therefore, it's at Y when the future is rewritten and sent to the DBT.
True. Chrono Cross confirms this by saying that the future is analagous to a collage of possibilities, depending on the actions taken by people in the present. But we were discussing the possibility of Marle not having to disappear at "Time Y" as you name it, or at the exact moment that Leene dies. If the future is undetermined until people make actions in the present in the Chronoverse, then what if the actions of some random soldier in Guardia castle for example make it 100% certain that Queen Leene would die in the future? Would Marle disappear at that moment or only when Queen Leene disappears? Why not at that exact moment, as that would be the first link in a change of causality that would ultimately lead to her death? Or would she disappear if Crono and co. would save her anyways?