Ah, I see now. The vertical view does not wrap schedules to the next day. So, Tuesday's shift actually does start on Monday (in week view you can see Chad's Tuesday shift has a off queue block that starts before 12am Tuesday due to post generation shift manipulation) and we show it on Monday's line in vertical view. For the vertical view the day the shift starts will be the line it is on and, in this case, Chad has two Monday shift starts: one at 12am and another at maybe 11:45pm.
Image shows a line from 12am with Tuesday shift starting before midnight.