Yes, that is true. The frame is slightly different from the Colt. Probably the only way this would affect you is if you decided to put on a Wilson beavertail grip safety or one with the same cut radius as a Wilson.
Other than that - everything else is pretty much interchangeable with aftermarket parts. I've done this myself, and have changed out literally everything on Kimbers.
Kimber's aren't low end? Well, ummmmmm......to ME, a standard Kimber Custom IS low end. Of course, I'm excluding the other ones out there that are lower than low end - trash and paperweights.