I guess it refelects the increasing tendency to want to legislate every aspect of the flight.
this tendency can also be seen on the north sea where the ops manual is well thick in its attempt to cover every possible scenario, in the long term removing the commanders discretion.
having said that I still reckon they are actually sensible figures that have been arrived at.
I think it is a slightly blunt instrument though, I know one high time instructor who is actually a PPL under grandfather arrangements who am I sure would be competent at 800m, and at the same time I know newly qualified CPL's who I would be distinctly unhappy letting them go when there is 3k.
eventually people are people and whether they have a private or professional licence does not neccesarily indicate ability.