I unds if you guys believe it is hypnagogic hallucination. I have researched it for awhile and true it can happen to any of us. But for me I already knew when I see them, then I knew something going to happen and it happen alike they warned me of something. For instance today at work, I was busy and focus on work then for a second I saw an angel in my mind then I knew something is wrong. Well it did something happened few hours later, good thing it was not too serious, our tree fell down after a powerful dust devil knock it down ( away from our house and fence and next door, whew). So do call me nut when I see angels once awhile then I knew I am being warned of something ahead of me.
I do not believe kids image those things, they do not know what image is or able to tell adults about it. I remember my then three years old son told me some bizzare stories and where does he get those stories as he never saw or heard of them before. He has not read book or know about them. I asked him now about them, he does not remember but I do remember what he told me few things. I would not share this one here because it happened to me and he saw it. I do not even know or remember then till 10 years ago. Now I unds why little kids are not sealed till they getting little older. We are meant not to remember or see them. It is better this way for us all human beings that we do not see them.