I'm not so sure though it's a product of it being more west...I think it's more of how it evolves the low pressure. The 12z run has a much more mature surface low and is pretty much nearly perfect cyclogenesis. So I think the talk of models being "west vs east' is not necessarily correct...it's a matter of how the area of low pressure evolves.
I am kinda torn on this. Looking at the ulvls the dynamics are quite impressive and support a great deal of ulvl divergence. However, given the stationary front it's more likely you'll see multiple areas of low pressure develop along it. Is it possible the NAM is going crazy with one specific shortwave or low? Very possible. Could it also be heavily influenced by convection? Possible.
At this juncture I think I'd be less inclined to side with the NAM right now until there is additional (stronger) support. I would think one axis of very heavy rain tied right along where the best dynamics/forcing are...which is east of us. However, that ulvl jet structure is eye opening.