I do not think peak grade is better than anything else.
I do not know what gave you that idea.
I'm told that this went through the WCF MC and was voted in by WCF Members. I think what it shows is how hopeless croquet committees are at doing the right thing and then how hopeless croquet organisations are of advising their players of changes.
I'm not quite sure why you think peak grade is better than current grade or average of annual grade or another variant.