Golf ball distance is not currently limited.
False. Golf ball distance has been regulated since 1976 and golf ball rebound characteristics have been regulated since the 1940s. In 2004, the USGA updated its testing methodology to more closely reflect the athleticism and clubs of today's Tour pros. All golf balls played on Tour and the vast majority of golf balls sold have passed the USGA’s distance limit test.
I suppose this is a misconception not a myth. Though I don't know of anyone who thinks that players are using non-conforming balls.
Does anyone out there actually subscribe to this "myth?"