The fatigue rules have been under “review” for decades, and will continue to be so for decades.
It’s like classification of operations.
The required decisions are political, not technical.
As Sir Humphrey so eloquently stated when discussing the role of government and the bureaucracy:
"Two basic rules of government. One, never look into anything you don't have to. Two,
never set up an enquiry unless you know in advance what its findings will be"
A bit of digging into the little consultancy involved is an interesting insight into motivation..