Did you notice that the guy's harness had the carabiner clipped to the shoulder strap for stowage?
That is a critical error.
Never clip the carabiner to anything, even for transport.
In the event you fail to clip in, you will want the carabiner banging against you.
It is the last hint that you are about to die but can still abort.
Of course, you can always clip in, visually check your connection in and do a hang check.
You can also do your first hang glider flight on a training hill by yourself.
It worked for me. And it was awfully exciting.
So was my first high flight.
I don't know why people give that up to fly tandem.
For me, hang gliding is a solitary sport, a game of chess between me and nature.
I don't fly tandem.