I guess I need the time for on-board narrative, since one of the characters cannot leave the ship for plot reasons, mainly needing advanced holoprojection to manifest.
I guess in my mind having the ablity to cross such vast distances without any flight time just does not make sense in a story, but makes perfect sense in game.
ARTISTIC LICENSE! I WANTS IT!
My interpretation of the near instantaneous transfer is closely tied to the reference to entering "witch space." Note, I haven't read any of the fiction aside from the first half of Dark Wheel so this is pretty much all from my in game experience
Contention: Traveling between stars via witch space is not 'travel' per se but more of an inter dimensional teleport where speed no longer has meaning.
exhibit A: When you travel between two systems, your speedometer goes absolutely nuts. You could interpret this as being like your speed is constantly going off scale, like one of those circular weight scales spinning all the way around...but that makes no sense for a digital display. Instead I would argue your speedometer is trying to figure out how fast you are going and it just has no eartlhy idea.
exhibit B: When you travel between stars, it doesn't matter if you're just hopping to the closest possible star or going 35 ly in your anaconda, you will see stars streaming by you and nebulas dancing around in all directions. It's almost as though travelling through witch space is making you exist everywhere at once before finally dropping you back into reality.
exhibit C: there is no correlation whatsoever between how long you are in witch space and how far your destination is. Most warps last the requisite 15 seconds tops, but I have had my warp kind of get stuck for a full minute in the past. This obviously was because the server was having a little trouble loading that star system, but from an in game perspective you can see time and distance lose a lot of meaning.
Conclusion: For artistic license, you could argue that normally it takes 15 seconds to a minute to get through witch space, but what if something goes wrong? Maybe an FSD malfunction can leave you stuck in witchspace for an hour while your computer tries to track down the problem and properly orients you back in reality.
It's a thought.