I can only echo what has been said by others that performance is nothing to do with grading most of the time, handles to me are just as important as pressing, a very stiff handle of badly fitted can make a bat feel like a plank and so can under or over pressing, Im using a bat this season with 7 wonky grains, but it's a UK made GN so has a very good handle and pressed very well, probably be a grade 2/3.
@simonmay5 must have 50 bats or more, including special bats such as a low density H4L monster yet his match bat is a butterfly because it performs perfectly and works for him.
Ultimately a bats performance is down to pressing, handling and the user, I've seen people make guns looo like planks and planks look like guns. The only exception is if a brand chooses to grade on performance though I see this just as a way of up grading ugly pingers to make more money
There may however be some correlation for less experienced or smaller bat makers that they take far more time with their higher grade clefts as they've cost them more from the supplier and therefore they don't want to waste them, also lower grades with a knot of similar under the face will make the bat seem very hard but these are more exceptions to the rule rather than the norm