That all said you are correct, they use the limits as targets but why wouldn't they? It is the same as max takeoff weight, Max landing weight, Max zero fuel weight etc
People are not machines.
Virgin has been using a FRMS quite successfully since 2007 ish and it works as well as can be expected.
So does Jetstar allegedly. Its based on FAID which was built for the trucking industry and is not scientifically based.
We as pilots are still miles in front of junior doctors who works crushing shifts and they too have the power of life over death - doesn't make it right just making the observation
The medical profession kills way more people than aviation. Medicine is slowly waking up to that fact.