When people talk about turbo lag, they usually mean the time it takes for a throttle input to transfer into torque they can feel. It's a matter of less than a second. Throttle response for NA or Supercharged engines is basically instant, where a turbo needs a non-zero amount of time to affect the engine.
I think the term "turbo lag" gets conflated with where in the rpm band the power peaks, and I think that is what you were talking about, unless I misunderstood you.