OS uncertainty.
When a new processor comes out, the OS won't know what to make of it until an update comes out. An x86 processor has two 'identifying' strings. One that is just a set of numbers that identifies the 'family', 'model' and 'revision' of a chip, and another that is a plain text string that generally isn't formatted very well. (For example, a Core 2 Extreme, Intel's top-end desktop chip, has a 'CPUID' string of 6F5, and a 'Specification string' of "Intel(R) Core(TM)2 CPU X6800 @ 2.93 GHz") Neither look very good in an 'About this Computer' box.
So Apple takes the numeric string, and looks up the name of the processor. It then displays the 'friendly' name. Well, the OS must not have a processor for that CPUID yet.