Going to disagree with most here. Yes, the entire issue could be as simple as crown of the road. OTOH the OP presumably has other bikes or remembers other bikes that don't pull.
Most bikes are not perfect out of the box. Most bikes will not do what they should do until a lot of tuning has been done. This one it does sound like an alignment problem. String test is very crude, won't catch much. The store should have done a thorough alignment check and should have walked their customer through the process, making sure he knew what they were doing and what they were looking for.
Giant frames are not particularly accurate. Yes, frames on $4000 bikes can be off. Most will never notice. Most have very low standards. Not a lot of impetus for manufacturers to correct problems that few will ever perceive. Off the top of my head Look and Time have reputations for making accurate frames. There must be others. Giant, Trek, Specialized, Cannondale do not make accurate frames. If customer is very picky custom is a live option. For $4000 it is possible to do a custom and a basic build.
Buy a new bike from the oldest family-owned store possible. Best is an owner who has built frames. No, that is not always possible. Yes, it can be done. My LBS is owned by a man who has built a few hundred steel frames and was part of the team that designed and built the original Kestrel, the first monocoque carbon frame. He has very little business. Consumers want to buy from the big factory owned Trek store. Buy a carbon frame from Ron, you get hours of his time. From a guy who has literally forty years experience with carbon. The other two LBS that get some of my business the owners have also built a few steel frames and know what alignment means.
The bike business in general has extremely low standards. Anyone who has high standards is pushing uphill. You can still get to top of the ill but it won't be easy.