User blog comment:Brianbreed/The Biggest Single Plot Hole in Mass Effect 2/@comment-1388547-20110910024820

All I can post is speculation, but perhaps something about the physics makes the core hazards mostly dangerous only to ships exiting a mass relay jump? Either that, or perhaps it's just a matter of dodging the debris field immediately surrounding the relay, which the Normandy can navigate past, now that Joker and EDI have had time to gather sensor data.