I think anyone trying to grade bats on performance, rather than looks, would be nuts. Who would want to but a 'plank grade' bat? You'd never sell them. Obviously 20 tight grain clefts are rare, light in weight clefts are rare, super clean blemish free clefts are rare, and when anything is a scarce commodity it attracts a premium price. My take on it is that clefts are pre-graded before they get to the maker, so in some respects the maker's hands are tied on what grade a finished bat might be if they are working to a profit level. However, pre-grading at cleft level isn't an exact science. As we all know L&W bats appear to put on weight once they reach the UK, so there is no reason that raw clefts, even expertly dried, can't do the same thing.
As regards tapping up a cleft, then a finished bat, I'm obviously no expert but to me it's still in the lap of the gods if it will perform on the pitch. As Paul Aldred said, he had a DF that just wouldn't go. If you look back on this forum, these bats are a lot scarcer than bats that even perform adequately (which if you take a non-cynical view are themselves hugely outnumbered by the 'absolute guns' that forum members own).
And then there's the factor of the guy holding the bat - as Garrett wisely says.
I'll fess up, I've got a lovely Salix Pod that I just can't get on with. Yes it's light at 2-7 but I can't get the ball off the square with it. But I've loaned it to guys who usually use bats in the 2-12 range and they've hammered the ball to all parts with it. There's nothing wrong with the bat, it's me. These are younger, fitter, more talented guys, and it shows.
On the plus side I've used slightly heavier bats (2-9/2-10) and can score a few runs, proving, really, that a heavier bat will hit a ball further and to an extent timing and bat speed has b/a to do with it.
I'm as guilty as anyone on here for having an eye for a well shaped piece of willow, and buying more than I need. But, you see, I'm old, I'm raging against the dying of the light, I'm searching for a bat that will allow me to hit the ball as far and as hard as I did 25 years ago. I'm obviously deluded, but perhaps no more so than someone who thinks that a professional grade bat will make them play like a professional.
And just because test player A has a preference for x number of grains with a strip of heartwood on the outside edge, it doesn't mean that these are the ideals for any bat. In most professional sports there is a huge amount of superstition - if you factor that into the equation you might be getting towards a more realistic view on why some players prefer the bats that they do.