[transient]

Ok, think of it this way. When the clutch is engaged (pedal out) then your engine is directly connected to the rear wheels. That means that if you're not moving, neither is your engine.

Auto's are set up differently. Instead of a clutch, there's a torque converter, which uses ATF fluid passing through it to transfer power to the rear wheels. There is no direct connection between the engine and the wheels (until torque converter lockup).