I believe that both a "Blue/white Game" and a Late-night type of thing can be classified as an open practice as opposed to a scrimmage.
UNC has settled into a routine of having the MBB Blue/White game occurring on a home FB gameday, set to start an hour after that game ends. I assume that they have concluded that having the women play first would put the FB and MBB game too far apart to entice fans to stay. (They are not going to run a WBB game concurrent to the FB game.)
And I guess WBB after the men's scrimmage would be too long a day for fans? Or the optics of most fans leaving would be bad?
But I do not know why they do not have a separate WBB Blue-white scrimmage. Unless it has been determined that the event would not break even revenue-wise or something, but I find that hard to believe.