Lesser and Piebalds crossings?

[Sprinkles]

Alright, now explain why he produced a Butter and a Butter Daddy off of Platty Daddy x Butter.

That clutch alone should disprove it being an allele of the Lesser gene.

Because butters and lessers are essentially the same morph, just with slightly different colors. Much in the same way that black pastels and cinnies are the same gene from two different lines.