Listen To The Pro's!
I think that this comes down to precisely what Scroggs and 727man have already tried to explain. IMO You will always get those who have to work exceptionally hard to achieve the bare minimums, the same as you will get the others who's effort is minimal to achieve the higher grades (and combinations thereof). Can you distinguish who's who just by looking at a set of results? I think not. This is why airlines (amongst other reasons) have interviews to discover a persons true personality.
To my way of thinking those who here who see fit to argue with the comments of our two seasoned proffesionals above, may need to look at there own personality. After all, they have the jobs and it will be people just like them on the otherside of the desk when we are going to interview.
As for the hours: well just ask the thousands of university graduates out of work or in jobs not befitting of their qualifications. Experience speaks volumes.
My conclusion: Give ground studies your all and achieve the best you can, but 75 is the number that matters. If the airlines wanted more they would surely ask.