Yes, that was the 2002 NEC. For the 96 (which should have the same number at the 99 code) the reference is 384-16 Exception #2.
The handbook commentary:
"The phrase "for existing installations" in Exception #2 means the existing panelboard. It is not intended that a split bus panelboard used in an individual dwelling occupancy be replaced if a circuit is added to the existing panelboard. It does mean, however, that for installation of new panelboards in new or existing residential occupancies, a split-bus six-disconnect panelboard (with more than two circuit breakers or sets of fuses protecting the panelboard ) is not permitted for the service equipment.