What is the use of trains that terminate at night?
I found 4 high speed trains Harbin-Beijing which terminate in Beijing at night:
G4722, originates 17:39, terminates Beijing South next day 1:36
G4724, originates 18:41, terminates Beijing South next day 1:52
D4608, originates 18:52, terminates Beijing next day 2:42
D4610, originates 19:22, terminates Beijing next day 3:05.

So, why? Does Beijing subway run to Beijing South and Beijing station at times of 1 to 4 at night?
With 7:11 to 7:57 travel time, it would make sense to have overnight trains, which depart Harbin at 23 or so and arrive in Beijing at 6...7, in order to travel by subway and show up at work somewhere in Beijing at 8.
It would also make sense to have overnight trains which travel direct from Harbin to Shanghai or Xian or Guangzhou, and drop off passengers when they pass Beijing at odd hours of night.
But why terminate services at night?