The name "white box", means the product will be sold in a plain, non original box. It might be white, or just a plain cardboard box. Pay no attention to the colour, this is just the term, a bit like "white label" when you used to buy underground vinyl records with just a plain white label on and no information. Yes the label was almost always white, but the term meant/means underground and not official.
Digital rev and importers use this term because the lens will have come from previous kits. The delay is probably because they buy in the kit they need (based on a combination of stock levels required elsewhere and whichever is most profitable for them to sell once split) and then "split" the kit and sell the lens off as "white box". The lens is brand new, it just has no original box. How the warranty works on this I've no idea...but then...it's imported anyway so.... I think it would be safe to assume you had none, but maybe DR can confirm.
I'm thinking of buying one myself. They actually for some time were sold for £200 and recently went up to £219.