Yes, the lulzbot dev team seems to have just done the first workable hack that came to mind when originally designing the mini. Presumably before they added the auto bed leveling feature they had a functional z-min switch. With the bed leveling feature this required them to replace the z-min stop switch with a red 5v wire coming from the nozzle (therby acting as a switch). The blue and black wires probably do indeed go to this redundant z-min switch. Why this switch is still wired up and included on Mini’s being sold is anyone’s guess and i assume just comes down to laziness. or perhaps some sort of internal testing procedure during assembly?
But the basic answer is that the red wire is the one you want in z-min. The blue and black wires theoretically could be ripped out completely without compromising any functionality.