No, that's not going to do what you expected. If you want to plot using date and time data on the X axis, turn that data into a datetime array first.
s = ['2020-11-17 13:03:00'; '2020-11-17 13:03:00']
In this case using the xline function is probably what you want instead of plotting using the same X values twice. That will keep the line spanning the whole height of the axes even if you pan or change the Y axis limits.