This is definitely my preferred method. And reverse it for launching; everything and everybody but me in the boat, plug in, switches on, ready to start before we back onto the ramp. I back the boat down the ramp, unstrap, wife backs boat off trailer and waits for me away from the courtesy dock, pulls up when I'm back from parking the truck. On and off the boat ramp in 2 mins or less. If the trailer parking area is empty and I know she won't have a problem pulling into an easy spot with the truck/trailer, sometimes she parks the truck and I use the time idling the boat to fill ballast bags.
I can't stand folks that back their boat onto the ramp (especially during busy times) and then have a 5 minute fire drill loading ice chests, boards, bags, etc. onto the boat. We saw some folks doing that shit in a late model Wakesetter last weekend, which solicited a nice eyeroll and commentary from my wife. Now that I think about it, my wife talking shit about other folk's boating techniques is kind of a turn-on. So maybe I like folks clowning around on the boat ramp? Deep thoughts...