This is only my opinion, but I wondered if it was a sort of generic term, like Philodendron Schott- but let me hasten to say taxonomy is not my field at all!
I do have a special interest in Zantedeschia, however. I know the name Zantedeschia hybrid or 'Mini Callas' don't sit well with me, they are not worthy of these beautiful plants. You just don't see other hybrids or colored flowers referred to that way. As an example, tulips have many varieties, they are listed as Tulip 'Apricot Beauty' or whatever, not Tulip hybrid 'Apricot Beauty'.
Zantedeschia are so confusing to the average (US) gardener- Giant Calla, Mini Calla, hybrids- grow
them in a pond, don't let them get too wet, I get questions about them all the time. Those of you on Dave's Garden or especially Garden Web know what I mean!
Something should be done with the names- if nothing else, it will make them more marketable!