Come now pj123 you're splitting hairs a bit here aren't you? You're well aware what next working day means for deliveries.
I appreciate your point but most delivery workers, I suppose most workers in general work Monday to Friday 8 to 5 or 9 to 5 or something similar. If they work Saturday its maybe overtime or occassional days. I realise there are exceptions such as shop workers and factory workers etc but when they say next working day you know they mean Monday to Friday.
Otherwise they'd just call it next day delivery, which would at present be impossible to do because as far as I know van delivery drivers don't deliver on Saturdays normally, except perhaps special delivery and certainly don't deliver on Sundays.