Great find!
Policeman = lack of rep meaning your friend got invited and you didnt and thats possibly why, thats straightforward enough, rep counts.
Rep = better missions and tip-offs so may be just referring to some of these.
Secret Organisation - Dark Wheel obviously stands out but yes Permits and maybe Engineers count as well. If 'lots of people get invited and you know you haven't been' how secret is it (reference to Sirius & Yoru ranks maybe)?
I agree it's likely related to locked systems/bodies and permits, as well as Engineers, but it also leads me more to the conclusion that they have a certain methodology for measuring a CMDRs rep for X to allow Y access/permit/unlock. So it's probably unlikely they'd invent something completely different for TDW, it's much easier to use similar methods, but perhaps more complex requirements than re-code something different within a game mechanic.
Raxxla, now that's a different beast - but I've always been focused on TDW as a path towards that destination.
/ Ra.