I don't understand very well which your point is.
I kept in silence my day dreaming activity. I felt ashamed for having fantasizes and even believed that it was something I had to cut if I didn't want to get mad. But, I needed it.
I agree with you in the functionality you describes for day dreaming need.

I remember that since the first moment I met my partner, suddenly, I never felt the need to fantazise again.
Sorry if I didn't contribute a lot to your topic. Only adding my own experience in case it can be helpful.