I’m inclined to agree. I was raised in the Texas panhandle and called Dallas home for years. Tea at restuarants was always served sugarless, and waiters never asked if you wanted sweet tea.
Here in Florida, they do, and it’s too sweet for me. I order unsweetened, then sweeten it.
As to lemon slices, I stopped for lunch at a Coco’s restuarant in Green River, California and had iced tea with my meal. I squeezed (squoze?) my lemon slice into the tea and drank.
The waiter saw me and said he’d never seen anyone squeeze the juice out of the lemon wedge before. I asked how he got the flavor into the tea otherwise. He said he just put in lots of wedges. LOL