I'm very confused about the meaning of「Vておく」after watching this video.
I usually interpret「Vておく」as "to do something in advance/do in preparation for future." The speaker in the video mentioned that it is not always true. He said that「Vておく」actually means to do something and put the results in effect. I'm not sure how it's different from doing something in advance. He provided some examples where「Vておく」doesn't mean to do something in advance.
It's cruel to lock a child in a room.
He mentioned that the「Vておく」in this sentence doesn't mean do something in advance but do something and leave its effect in place. If I think「Vておく」in terms of future preparation, I can understand this sentence like this
It's cruel to lock a child in a room (to torture the child or something).
Which of the two interpretations above correct? You can see the second interpretation directly contradicts the fact that「Vておく」don't always mean to do something in advance.
It's alright to let a baby cry sometimes.
Once again, he mentioned this「Vておく」doesn't mean to cry in advance. But, I can interpret it in another way. In terms of future preparation, this sentence can also be rendered as
It's alright to let a baby cry sometimes (so that the baby can calm down).
Should I always interpret「Vておく」as "to something in advance"? More precisely, does「Vておく」always carry the nuance of preparation for future?