Sorry, you're completely missing the point. There is inconsistent behaviour dragging outside the chart axis ranges when the chart is zoomed and when it isn't. Try it and see. It looks like a bug to me.
Adding the property does not fix the bug. I want to drag outside the axis ranges but the drag behaviour after zooming is confusing at best, so I would only want to disable dragging outside the axis ranges when the chart is zoomed. Hence, I need to set the added property based upon the zoom state of the chart.
Why can't you fix the inconsistent behaviour?