Yes, that's the correct explaination. Also note that in the early days of Pachinko, the manager would give a few hammer hits on the side of the nails of the ma

Yes, that's the correct explaination. Also note that in the early days of Pachinko, the manager would give a few hammer hits on the side of the nails of the machines to change their orientation slightly every night, so a machine that was winning a lot yesterday might not win a lot today. Nowadays they're electronically controlled and the nail position change automatically to vary the winning probability in a very controlled way.