I want to make an educated guess that Keil thought about this to some great degree. At the time this scheme was derived I am sure that there were few parts that had 2K of code memory. For years 4K code memory has been the prevelant small memory size on 8051 controllers. So Keil engineers may have reasoned at the 2K size from a 2K boundary so that you could not use the eval tools to make production programs for 2K processors and you could not make production programs up to near capacity for 4K parts.

I would not be surprised that if the scheme was designed today that they may have used somewhat different criteria. Look for example at the Keil bundle that comes with the Cygnal eval cards. That eval version has a different set of rules than the copy that you are able to dowwnload from the Keil web site.

Michael Karas