I wouldn't be overly worried about where it is but the aesthetics of a blade will draw people in....
The stain is harder and stronger so if hit in the area of stain it will absorb less energy and therefore more energy will be returned to the thing, ball / mallet, hitting it.
To quote Quilt Winders and Pod Shavers and Len Newbery managing director of Grays Nicolls until his death in 1976 father of John Newbery who taught the likes of Julian Millichamp, Andrew Kember etc
"The timber of the salix alba caerulea is distinguished by a bright orange stain that is known in the trade as the butterfly stain. when these stains appear on the blades of bats the players often reject such bats thinking that they are faulty whereas they are the hallmark of simply the finest willow."
[C.G Bussey Cricket bats] George Bussey said "The finest Blades are prodcued from timber having this 'stainy' mark"