Probably a good rule of thumb.
See, thats the only difference I can even corner down on a regular basis, yet I'm terribly confused by the fact that the MIM factory doesn't even make necks. In fact, all MIM Fenders have MIA necks on them.
But there is certainly a difference, my guess is they use lower quality woods for the ones to be exported?
MIA necks are a tad wider and have rolled edges. It might account for the difference in feel.