Applies to all passes with chosen days-and it is even clearly in the general info; ON a chosen day you can use any train (in the system) that day-board till 23.59 last and -if it does a long run-stay in that train untill the end or goal. There have indeed been some reports of utmost clever persons who started at 0.03 in an overnite, travelled all day and used a 2nd overnight-board 23.33 and use till far end-next day around 14.00.

Note however that the nr of overnite trains is far smaller as non-EURos tend to think and that all these trains must be REServed