I find this to be true, in my case. Experience helps though and without experience Ni will stagnate so if experience = data, the more the better, for accuracy. I often wake up with an answer to a situation after sleeping on it. My processing seems to work better while I am sleep. It might be different for Ni creative or other types with stronger Ni. The dream world is a timeless place so I am able to piece things together without pressure. I can move in all directions and step outside of the experience of time to work stuff out. I literally have all the time I need while sleeping. I have lived lifetimes from birth to death in a span of a few hours (our time). Then I will wake up with more cohesive (coherent) ideas that I feel confident to speak about.
That is how I can wake up and know just what needs to be done about a problem or how a situation is going to evolve. That is why some people have thought of me as a "psychic". I am not able to just tell people their future though without any information about them like a other "real" psychics. I can't even tell my own future long term. I do know all probabilities for myself in the foreseeable future though. I don't even like to make any long term predictions for anyone because I feel I might influence their choices and lead them down the wrong path. I tend to stay quiet unless asked and sometimes even when asked. I do not like being wrong so I do pick and choose what I will say.
If I have high confidence in what I am sensing then yeah I will probably tell them, unless it is really bad. My sister says not to tell her bad stuff anymore because she doesn't want to know. This was after a few bad dreams I told her about came true.
Sometimes I make a lucky guess about someone I don't know. I don't like being asked to predict things by people I don't know. Of course I am better predicting things about my own family members, people I have know longer and situations I have subconsciously witnessed for awhile. I have been watching their patterns for a long time. It makes what I say sometimes seem prophetic but it is probably just long term pattern recognition, to my disappointment. I didn't know much about Ni and pattern recognition when I was younger. It takes all the magic out of it for me.
It still impresses some people though who have never looked into these theories. Do I tell them? Not usually. It is not something I feel I can educate anyone on in detail. I also like to keep some mystery. I have explained it to my family though. At least those who are willing to hear about it. Most would rather maintain the mystery for some reason.
I don't know if my explanation of Ni makes it any less mysterious anyway since it is hard to explain to those who do not use it as a base function. Those who do, no words are usually needed. We just sort of acknowledge each other in indirect ways, most of the time. It's not like we spend our whole days predicting outcomes or whatever. We have lives and other stuff to do. The one type of prediction I do that tends to irritate some people and delight others, is watching a movie and predicting what will happen next. I have practiced being silent but sometimes it is so hard. I watch a lot of movies so it isn't that hard to pick up patterns in them even if they have different writers, directors and producers. Themes are easily noticed so knowing what comes next isn't hard. If I am stumped by a movie and can't tell what is going to happen it really bothers me on a deep level. I kind of feel lost if my "prediction" is totally wrong. It also make the movie a bit more enjoyable sometimes. I will just relax after my attempts fail and just watch the movie.
It is harder to put into words while I am awake and focusing on something than it is to allow things to come to me spontaneously. I don't like being put on the spot to answer things because I don't always know how to say it in a way that others will understand and not just roll their eyes so I wait for something to develop and then I can put it out into the world. Writing for myself is an exception. My diaries are filled with things that flowed easily because no one was putting me on the spot. :/
I assume I am taking in information, constantly, and a lot of it subconsciously, while awake but in order for it to make more sense I need to sleep. It is like a "whoah, that is my answer" kind of thing. I know I can do Ne too but it is very exhausting to do so and I prefer to filter out all the possibilities and go with what is most probable based on the information I have sorted. It is a time saver. Brainstorming is not my strong point but I don't feel I need to since I will get my solutions and answers my own way.
I turns out, after some testing, my memory is actually much better than I thought it was.
Didn't mean to ramble...