i've kept ferrets a long time 39yrs,all we kept when i was a kid was white's because all we did was ratting and i've never come across any defects in any i had,
i dont think there will be any white's out there that have not got polecat in them, just because it's white does'nt mean it's not 1/2 or 3/4 polecat.
when there deep in the burrow the only thing there using is there nose,and when a rabbit bolts with a ferret on its tail it does'nt come out and have a look for it,it should put its nose down and scent trail it, dont want mine going bird watching thats for sure