In a traditional AC unit, heat is produced by either electric strips or by a gas burner, no refrigeration circuit is involved in the heating cycle. So, just a blower motor runs, compressor (and condenser fan) never runs in the heating cycle.
In heat pumps, refrigeration circuit does both heating and cooling. So, compressor works in both cycles.
One can install an efficient AC unit with electric strips (gas burner) with "efficient ECM motor (for air blower) + VFD compressor (single phase to DC to three phase AC with variable frequency) + modern controls to manage both inside and outside motors." That's where modern AC units are driving at.
Heat pump uses electricity for compressor fan and fan in that outdoor unit. In an efficient conventional AC unit, one trades the extra electricity used in the outside unit for the electricity used for heat strips.
Geothermal heat pump is efficient and is a different ball game.