I sad I wasn't going to post any more opinions
but here goes.
I don't think our hair grows unevenly. I think that it may look or be uneven is because our hair grows "out" and "down". So therefore, if it's growing 6 or 10 inches straight out like an Afro, then if you have 6 inches on the crown and then the same 6 inches on the back, well, then back will appear to be longer and the crown will be resting on top, creating a layer.
But it's the same inches. That's why I measure by inches, not by SL, APL, etc. Not till I get a longer length on my hair, then when I cut the back, which is between my shoulder blades, then it would be even with the rest of my hair. But I won't do this till I at least start getting some real length on my hair.