AC always has external components.

Your taxpayer doesn't have Central AC if they have a Split. That's a difference.

AC components are external to allow the condenser to shed heat.

A Split component that is internal would be the wall-mounted vent with a fan (distribution controls), sort of like you see a wall-mounted radiator (although it's not a radiator). A central system works with duct work (integral and multiple distribution points; may have zones and zone controls) and not direct to a vent unit that is internal.

Think of it as: Split = one to one (external to internal)

Central = one to many (external to internal)

That's a basic overview.

A Split system would not be treated as two parts. A central system might even have three parts, now: Heat, AC, and HRV/ERV (efficiency recovery).