Some endorsing punk rock artists demand an F string between M and G. According to them this is required to make super fast hardcore punk a lot easier to play.
This in turn led Jackson, in their Charvel line, to create a short-scale version that places a W-tuned string over a T string, while retaining the Ibanez idea of a third string. Taking advantage of the new Ibanez-speedpunk-inspired tunings, the third string is an F.