Yes, that is correct.
One more question on pre-roll.
If I have pre-roll greater than 0, does the gap between flows need to be larger than the pre-roll number?
This seems to be required. I have a case where there are three grace notes leading into the first note of the flow, and pre-roll is set to 0.4. If the gap is 0 then the grace notes play back with no perceivable time. If I set the gap to 1.0 then it plays back as expected.
Yes, that would make sense, since all of the flows are arranged on a single timeline.