What this means in practice
Some tasks cannot move to software no matter how capable the model, because a licensed human must legally perform or certify them. The rollup formula subtracts for this constraint: regulation and safety accountability act as a structural brake on displacement.
The contrast is sharpest between exposed-but-constrained and exposed-and-free roles. Court Reporters face heavy speech-recognition pressure, but certified transcripts are a legal product that courts still require from credentialed humans. Air Traffic Controllers carry even stronger versions of the same brake.