When the Chinese SKS was really cheap, $60 - $70, It started becoming popular to convert them for detachable magazines. In 1993, the ATF made a rule that the ATF has to be notified of any firearm converted from fixed to detachable magazine. This has nothing to do with the 1994 AWB. The rule does not ban the conversions, but the ATF might deny permission to perform the conversions. But the rule doesn't ban the conversions. It looks like more of a way to keep up with detachable magazine semi auto rifles, for future regulations, such as the 1994 AWB. Especially if companies bought hundreds or thousands of $60 SKS rifles and converted them. The rule itself does not ban the conversions and simply requires that ATF be notified of them.