[karcey]

G'day Medic, Welcome to the forum.
Your second diagram is correct. The string ball doesn't get held down by the pin. If this was the case the pin would have to be hammered in super tight. The string with the ball slips through the hole and then the pin is put in lightly after it. The pin effectively blocks the hole so the ball can't come back out. The pressure that the string and ball put on the pin is all sideways, so it doesn't drag the pin out, but when you want to change strings you just relax the string and the pin should come out easily. Never hammer the pins in. It's totally unnecessary.
If you think about this, and still have a problem, then ask again and someone will try to explain it in different words. But sooner or later you'll see that the pressure of the ball is on the underside of the soundboard, not the end of the pin.
Good luck with your playing, and keep in touch.