From my experience those who get firsts are generally no harder workers than those who get 2,1s or 2,2s as there is little real difference between them beyond marginal grading brackets.
The established rule is in fact that 1sts are obtained by those who 'do well in exams' (often a little weird), and they are often the type that are least competent generally, just the type that can pass exams. It certainly shows little else.
I read a good article once that 2.2s reflect a more rounded student who actually balanced themselves and their life better at University.
Now though in this age of Universities popping up all over the place and cashing in on the limitless horde of often vacant-minded students, it's more relevant WHEN you studied, as everyone knows what a conveyor belt process getting GCSEs, ALevels, and Degrees became after the mid-1990s.
The best employers look beyond the always subjective exam grade, so as long as a student gets their degree and builds their experience from ground level, they should be looked at as favourably as anyone who happens to have got a first.
I've known many students choose the easiest degree modules in order to get a higher grade, so it can really be meaningless.
Trust me