Originally Posted by
DrIsotope
I'm going to give the guy at the LBS the benefit of the doubt, and assume that when he said twisted he meant crossed-over. When fishing the cables through the downtube, it's pretty easy to cross the FD and RD cables over one another, so they would be rubbing, and result in poor shifting. It's not entirely uncommon for pre-built bikes to come from the mfr. this way.
As to the cables breaking off at the hood, unless you have older Shimano levers (like say 5700/6700,) or haven't changed the cables in a decade, it's not much of an issue.
I wouldn't be so quite to dismiss the mechanics assessment. If you look at the cable housing on the left shifter in this picture, you can see a bit of a twist in it.
noodles small by
Stuart Black, on Flickr
It started to shift poorly and when I took it apart, the rods inside the outer plastic sheathing had broken loose. The ends of the rods will come out of the ferrule and cause the cable to jam. This isn't the same housing but it's the same problem
IMG_1361 by
Stuart Black, on Flickr
This is what it looks like without the ferrule
IMG_1362 by
Stuart Black, on Flickr
The housing in both cases had an odd "twist" to the housing.