There might be a subtle but important difference in wording down here.
I can't imagine people showing up with food in either instance. I would definitely find it odd/rude.
Old-fashioned Greeks have the habit of bringing sweets when invited out, and the host is expected to serve them. The result is that the dessert course can consist of 3-4 mismatched, inedible sweets. You either ask guests which sweet they want or serve them a little of each on the same plate. But in the beginning I found it incredibly strange, quite rude and it still bugs me sometimes.
OTOH, I disagree with Miss Manners about wine. IMO, it is perfectly fine to bring wine, and it is not brought to be consumed that evening, but for the host to consume at his/her leisure. Sometimes I will bring cognac or whisky instead as a hostess gift. It is usually appreciated.
every one of those points i can relate to... we hosted a couple grill outs last summer and