I didn't know this but the Lexus IS Website is very intuitive when building a new 07 IS. It seems that the zipcode determines what vehicles are availiable currently in that zip code area.
Here in AZ there is only premium and x plan cars. In upstate NY there are sport and luxury packages availiable. Very interesting.

 

Same here in Hawaii.

 

This is nothing new. Most car company websites ask you to input a zip code before you build because different models and inventory are available at different places.

 

the options that are normally allocated to local dealers match that on the website. This was confirmed when I was at a dealer and they showed me what options they normally get allocated.

 

It has to be that way. There is no way you can have all combinations of all configurations going to all dealerships across the country. Honestly I don't think it decreases sales that much and if you want a car of a different configuration there are at least 2 known ways to get one.