Honestly? Because I want to get you guys together and if you were heading further up while also moving against the grain and in an area not overrun by cultists that would put you a few kilometers distant from the rest of the group and at first I figured I would have to work a few groups to get everyone together, Crayt's and Muse's posts allowed me to find a location that put them all within 1 kilometer and I did not want you to just be kind of meandering around on the other side of the hive working you towards everyone else while they enjoyed an action filled escape as khornate cultists fought against arbites and imperial guardsmen all around them as they fought desperately to escape collapsing buildings, gunship strafing runs, and fought battles against droves of enemies of various caliber.

I am a better world builder than a GM honestly I made a whole sector and it is pretty much your guys playground now. I could have had you off on your own doing your own adventure but as a GM I like having the group together as much as possible naturally and saw an easy opportunity to get the group together early on and experience one of my most epic events I have planned early on while simply writing off your character as having been taking a kind of serpentine route through the mid hive, not getting too close to the battle but also not heading back to the lower hive yet.