The security and quality control at the US Mint are very stringent. Misstruck coins almost never leave the mint and make it into public hands. They are embarassed when it happens.

The private mints that strike gaming tokens have much less in the way of quality control. They have to deliver the corect count of tokens to the customer but inspection doesn't seem to be anywhere near what it is with coinage. In addition, sometimes misstruck gaming tokens were made purposely and sold to collectors and dealers. Nobody seems particularly upset when this happens.

It would appear that Franklin Mint was much more careful in this regard, maybe because they have a history of striking foreign coinage and have a reputation to maintain. However, they lost out to lower cost competitors in the 1980's and no longer make gaming tokens, at least for US casinos.

In any event, gaming tokens that are imperfect seem to be more of a curiosity. They are collected but seldom bring big premiums as error coins do.