Welcome to the forums! It's great to have you.
I also run a low carb site so I do a lot of research into wine and health. I need to warn you first that any alcohol is going to interfere with a low carb diet. I say this as a fan of wine and as a low carber for 10 years. When I go off wine for a week or two, I lose weight. When I go back onto wine - just a glass a day - I gain weight again. So it has a powerful impact on your weight levels. Your body burns that wine before it burns anything else. So it "throws off" everything else you do.
Say you eat 50g of carbs in a day. Usually that might be a good balance for you because many of them get burned by your metabolism. But if you drink wine, that wine gets burned BEFORE your body starts doing anything else. So that same 50g might all become fat.
So it's not even the carbs in the wine. It's the alcohol - which is a body energy source and a toxin - which then interferes with everything else.
So with that all being said, even if you did extra exercise to make sure you burned off those alcohol calories and all you then had to worry about was the carbs, you discussed carbs per ounce vs carbs per glass. Those are two different measures. Glasses can randomly be 4oz to 12oz depending on who is doing the reporting. So you always have to compare apples to apples, with straight ounce measurements. And when you do, absolutely different wines have different sweetness levels. Some are incredibly sweet, Some are quite dry (which is wine terminology for not-sweet). But whether someone is guessing as to that value or actually measured it, you'd have to ask the winemaker. Also you can usually tell with your tongue