I would put this down to the play in the gearing between the hour and min wheels. it would be reasonable to assume that gearing made with older tooling would have more (or less depending on if they are stamped or cut) play than new tooling.
I have just had a play with
4 unitas/seagull 6498
3 2824s
and 2 A7750
and the 7750 has the most play in this area, and the seagull the least, maybe Ziggy or Francisco can explain if my theroy is correct and if some one can have a play with a swiss 7750 and see if that also has play.