http://www.inkjetmall.com/tech/attachment.php?attachmentid=1197&d=1470700983
Why was ABW designed like this? Roy's comment about the assumed editing space is the best explanation that I've heard. What really puzzled me was that it's different on gloss. This is the middle ABW setting on Ilford Smooth Pearl:
http://www.inkjetmall.com/tech/attachment.php?attachmentid=1158&d=1461312224
[I hope these image links work.]