No reason to assume that the father was a Butter when, indeed, he was termed a Butterscotch.
I agree that U.K. residents, often, utilize a variety of names to describe a cultivar............as do U.S.A. or European individuals, & on occasion the same combination of genetics are known by numerous 'catch phrases'.
However, Butterscotch may simply be marketing, in this instance, as there is no recognised cultivar by that name.
Is it possible that the sire of your Amelanistic hatchling has Emoryi inheritance & that is why the seller described the father as Butterscotch?
You will only be able to isolate the lineage once the breeder/shop owner proffers further details.