To make it clearer for newer guys...
Back in the olden days (2007-8?) Fractal had a different concept for IRs. The idea was to separate the mic from the cab, so you could pick a cab first and then choose the mic you liked later. To implement this, Cliff used a calibrated flat reference mic (Earthworks) to capture cab IRs as transparently as possible. Then he captured some common mics, and designed the UI so you could choose a 'mic type' to add over top of the cab IR (transparent EW capture). So if you chose the original Cali 4x12 (EW capture) and used the sm57 mic type, the result was pretty close to what you'd expect with physical cab and mic.
This made good logical sense back then, but it gets confusing now since all the new stock IRs have the 'color' mics baked in, and all the user cabs (3rd-party, producer packs, RW and OH) all have the mics baked in too. Today, it would make sense to remove the 'mic type' options completely to keep it simple. But we all know how hard it is to take anything away from Axe-Fx users. There'd be a huge backlash