Very interesting! Think about the use of lemon leaves in coastal Campania--not to eat but to use as wrapping for grilled items..
I've never heard of grapeseed oil used for frying in Italy-have you? Because most olive areas are also wine producing areas...(???) (But not vice versa)
Why? I think what greeks, turks, lebanese and other mediterranean cooks do with their grape leaves is fantastically tasty. I see no reason why eating the leaves precludes drinking the juice of the grapes -- unless the better the leaf, the worse the grape and vice versa. (Although the lebanese have produced both nice wines and tasty grape leaf dishes.)
I've seen dishes in Sicily where grape leaves are used in grilling fish to protect the fish and impart some flavor, but you don't actually eat the leaves.
I'm still curious as to why, with so many grape leaves around, Italians haven't incorporated them into their recipes, especially since they otherwise are so creative doing so with other foliage and whatever they can get their hands on!