In practice
The machine does the production work. A person decides whether the result stands.
“In the loop” means approval is required. “On the loop” means a person monitors and can step in. “Out of the loop” means the system runs alone.
This isn't the same as a person doing all the work. Review is cheaper than production, so 1 person can oversee much more.
Why it matters for product builders
People stop reading long runs of correct output. A checkbox that is always approved isn't oversight. Good review design must keep attention for the decisions that need it.