Start by separating the two names. IMCI is the worldwide package for managing childhood illness in an integrated way. IMNCI is India's own version, reshaped to match local needs, with the extra N standing for neonatal.
Where does the Indian version add something new? It pulls the very young infant, from birth to 7 days, into the fold, a group the original strategy handled poorly. It deliberately shifts weight toward caring for sick neonates and young infants. And it folds in India specific conditions in its case management.
Now the catch. The whole philosophy of looking at a sick child and addressing several problems together, rather than one disease in isolation, is the founding idea of IMCI itself. IMNCI inherits it unchanged. Because that integrated, more than one disease at a time approach is shared by both, it cannot be a difference, so it is the exception.
\[\boxed{\text{Treatment is aimed at more than one disease at a time}}\]