Thats not to say my parents didnt help me out with advice, let me live at home, etc, obviously at that age guidance and assistance can still be beneficial. But active control wont help at all, if your kid still needs it then you already failed him/her 6 years ago.
Your point is well-taken where it applies in actuality to helicopter or smothering parents, but the comments here are using “send them off” as a figure of speech. For instance, a father doesn’t really “give” his daughter “away” at the altar when she gets married, but the ancient wording just hangs around and warms the hearts of all who know it’s just a nod to tradition.
And in the sense that a young person is no longer residing in the parents’ house, eating the food provided or using resources shared by the parents such as cable or utilities, the parents are indeed “sending them off.”