On many watches there is no 3, because of a date window.
An eaten 6 is a creative way design of a dial.
Yes, the pocket watch heritage of smal seconds is the reason.
Should i buy a watch with an eaten 6?
No, because i chose watches with a central second hand.
Ever seen a Rolex day date with smal second hand in a dial?
No. Only a Daytona have it, and a yachtmaster chronograph.