looks like the ball does not go in with just pocket speed, apparently a more than firm hit is required. the cloth on the corners of the pocket are worn off!
The pocket is only a few millimeters larger than the ball. If the ball is directly facing the heart of the pocket,
(like on the head spot shooting into the corner, or center table shooting into the side)...
then in theory you could just roll it in.
But most shots are not perfectly facing the hole, the rail is at least partially blocking
the the shot from most angles. So to make the shot you must ram it so hard that it bends
the nipple, allowing the ball to fly 'through' the rail and into the pocket.
All those forced shots wear off the cloth on the nipples.
To be honest, though it's an interesting display of skill, I feel like the guys who designed the tables
were nuts and maybe didn't think it through. They blocked off shots from most angles.
Like a rail cut cannot happen, or shooting into the side from a steepish angle.
Did they really intend to make a game where most of the balls will end up "unplayable",
and even the routine shots from playable angles will rattle half the time?
Seems like a game for masochists.